Graham Corporation Annual report pursuant to Section 13 and 15(d)

Annual report pursuant to Section 13 and 15(d)

Debt - Additional Information (Detail)

Debt - Additional Information (Detail) - USD ($)		12 Months Ended
Debt - Additional Information (Detail) - USD ($)	May 01, 2020	Mar. 31, 2020	Mar. 31, 2019	Oct. 08, 2019	Dec. 02, 2015
Debt Instrument [Line Items]
Short-term borrowings outstanding		$ 0	$ 0
Letters of credit outstanding amount		13,328,000	8,503,000
Long-term debt payment requirements over the next five years		0
HSBC Bank USA [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Line of credit			$ 5,000,000	$ 10,000,000
Letters of credit outstanding amount		$ 7,931,000
HSBC Bank USA [Member] \| Letter of Credit [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Line of credit	$ 14,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Compliance		The Company was in compliance with all such provisions as of and for the years ended March 31, 2020 and 2019.
Assets book value		$ 128,281,000
Revolving Credit Facility [Member] \| Letter of Credit [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	3.00%
Annual facility fee	$ 5,000
Revolving Credit Facility [Member] \| HSBC Bank USA [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			3.00%
Availability under the line of credit		$ 2,069,000
Annual facility fee			$ 5,000
Revolving Credit Facility [Member] \| Maximum [Member] \| Letter of Credit [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Fee for outstanding letters of credit	0.85%
Revolving Credit Facility [Member] \| Maximum [Member] \| HSBC Bank USA [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Fee for outstanding letters of credit			0.75%
Revolving Credit Facility [Member] \| Minimum [Member] \| Letter of Credit [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Fee for outstanding letters of credit	0.75%
Revolving Credit Facility [Member] \| Minimum [Member] \| HSBC Bank USA [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Fee for outstanding letters of credit			0.65%
Revolving Credit Facility [Member] \| Prime Rate [Member]
Debt Instrument [Line Items]
Interest rate		3.25%	5.50%
Revolving Credit Facility [Member] \| 2015 Credit Facility Agreement [Member]
Debt Instrument [Line Items]
Line of credit					$ 25,000,000
Maximum limit of credit facility					$ 50,000,000
Term period of agreement		5 years
Interest rate description		interest at either: (i) a rate equal to the bank's prime rate; or (ii) a rate equal to LIBOR plus a margin
Fix rate to reduce fee on outstanding		0.40%
Availability under the line of credit		$ 19,603,000
Debt instrument, covenant description		Under the revolving credit facility, the Company covenants to maintain a maximum funded debt to EBITDA ratio, as defined in such credit facility, of 3.5 to 1.0 and a minimum earnings before interest expense and income taxes ("EBIT") to interest ratio, as defined in such credit facility, of 4.0 to 1.0. The agreement also provides that the Company is permitted to pay dividends without limitation if it maintains a maximum funded debt to EBITDA ratio equal to or less than 2.0 to 1.0 and permits the Company to pay dividends in an amount equal to 25% of net income if it maintains a funded debt to EBITDA ratio of greater than 2.0 to 1.0.
Percentage of net income to be paid as dividend if EBITDA ratio is greater than 2.0 to 1		25.00%
Revolving Credit Facility [Member] \| 2015 Credit Facility Agreement [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Unused commitment fee for borrowing		0.30%
Fee for outstanding letters of credit		1.20%
Revolving Credit Facility [Member] \| 2015 Credit Facility Agreement [Member] \| Maximum [Member] \| Dividend Payment Covenant [Member]
Debt Instrument [Line Items]
Maximum funded debt to EBITDA ratio		200.00%
Revolving Credit Facility [Member] \| 2015 Credit Facility Agreement [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Unused commitment fee for borrowing		0.20%
Fee for outstanding letters of credit		0.70%
Revolving Credit Facility [Member] \| 2015 Credit Facility Agreement [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.75%
Revolving Credit Facility [Member] \| 2015 Credit Facility Agreement [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.95%
JPMorgan Chase Bank, N.A. [Member] \| 2015 Credit Facility Agreement [Member]
Debt Instrument [Line Items]
Letters of credit outstanding amount		$ 5,397,000