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

Segment Information - Net Sales by Product Line (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Net sales	$ 22,178	$ 17,281	$ 17,224	$ 20,851	$ 25,624	$ 22,654	$ 21,126	$ 22,365	$ 77,534	$ 91,769	$ 90,039
Heat transfer equipment [Member]
Segment Reporting Information [Line Items]
Net sales									27,023	27,616	31,479
Vacuum equipment [Member]
Segment Reporting Information [Line Items]
Net sales									22,175	29,672	28,323
All other [Member]
Segment Reporting Information [Line Items]
Net sales									$ 28,336	$ 34,481	$ 30,237