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

Revenue Recognition - Net Sales Disaggregated by Product Line and Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Disaggregation Of Revenue [Line Items]
Net sales	$ 23,641	$ 17,198	$ 21,441	$ 29,551	$ 22,178	$ 17,281	$ 17,224	$ 20,851	$ 91,831	$ 77,534	$ 91,769
Asia [Member]
Disaggregation Of Revenue [Line Items]
Net sales									10,292	10,200	7,711
Canada [Member]
Disaggregation Of Revenue [Line Items]
Net sales									16,602	8,888	3,506
Middle East [Member]
Disaggregation Of Revenue [Line Items]
Net sales									2,610	3,785	3,160
South America [Member]
Disaggregation Of Revenue [Line Items]
Net sales									324	1,560	4,773
U.S. [Member]
Disaggregation Of Revenue [Line Items]
Net sales									59,441	51,950	69,166
All Other [Member]
Disaggregation Of Revenue [Line Items]
Net sales									2,562	1,151	3,453
Heat Transfer Equipment [Member]
Disaggregation Of Revenue [Line Items]
Net sales									24,785	27,023	27,616
Vacuum Equipment [Member]
Disaggregation Of Revenue [Line Items]
Net sales									34,461	22,175	29,672
All Other [Member]
Disaggregation Of Revenue [Line Items]
Net sales									$ 32,585	$ 28,336	$ 34,481