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

Segment Information - Breakdown of Net Sales by Geographic Area (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
Asia [Member]
Segment Reporting Information [Line Items]
Net sales									10,200	7,711	8,859
Canada [Member]
Segment Reporting Information [Line Items]
Net sales									8,888	3,506	8,702
Middle East [Member]
Segment Reporting Information [Line Items]
Net sales									3,785	3,160	11,039
South America [Member]
Segment Reporting Information [Line Items]
Net sales									1,560	4,773	2,558
U.S. [Member]
Segment Reporting Information [Line Items]
Net sales									51,950	69,166	57,027
All Other [Member]
Segment Reporting Information [Line Items]
Net sales									$ 1,151	$ 3,453	$ 1,854