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

Stock Compensation Plans - Stock Options Outstanding (Detail) shares in Thousands	12 Months Ended
	Mar. 31, 2018 $ / shares shares
Range 1 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price, Minimum	$ 15.22
Exercise Price, Maximum	$ 15.25
Options Outstanding at March 31, 2018 \| shares	18
Weighted Average Exercise Price	$ 15.24
Weighted Average Remaining Contractual Life (in years)	1 year 8 months 15 days
Range 2 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price, Minimum	$ 18.65
Exercise Price, Maximum	$ 21.19
Options Outstanding at March 31, 2018 \| shares	40
Weighted Average Exercise Price	$ 18.95
Weighted Average Remaining Contractual Life (in years)	4 years 18 days
Range 3 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price, Minimum	$ 30.88
Exercise Price, Maximum	$ 44.50
Options Outstanding at March 31, 2018 \| shares	11
Weighted Average Exercise Price	$ 33.28
Weighted Average Remaining Contractual Life (in years)	2 months 12 days
Range 4 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price, Minimum	$ 15.22
Exercise Price, Maximum	$ 44.50
Options Outstanding at March 31, 2018 \| shares	69
Weighted Average Exercise Price	$ 20.26
Weighted Average Remaining Contractual Life (in years)	2 years 10 months 2 days