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

Changes in Accumulated Other Comprehensive Loss - Reclassifications Out of Accumulated Other Comprehensive Loss by Component (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
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before provision for income taxes									$ (12,854)	$ 7,049	$ 8,730
Provision for income taxes									(3,010)	2,026	2,599
Net income	$ 833	$ (11,622)	$ 10	$ 935	$ 1,801	$ 1,840	$ 1,297	$ 85	(9,844)	5,023	$ 6,131
Reclassifications Out of Accumulated Other Comprehensive Loss [Member] \| Amortization of Actuarial Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before provision for income taxes									(1,050)	(1,387)
Reclassifications Out of Accumulated Other Comprehensive Loss [Member] \| Pension and Other Postretirement Benefits Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before provision for income taxes									(1,050)	(1,387)
Provision for income taxes									(233)	(490)
Net income									$ (817)	$ (897)