Business Segments - Business Segment Net Sales and (Loss) Income before Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue from External Customer [Line Items]
Net sales	$ 114,449	$ 103,886	$ 110,550	$ 103,516	$ 92,126	$ 82,861	$ 93,301	$ 63,578	$ 432,401	$ 331,866	$ 238,480
(Loss) Income Before Income Taxes and Equity Gains (Losses) in Joint Venture									(13,693)	(57,520)	4,520
Capital Expenditures									14,899	10,566	9,407
Depreciation and amortization									22,387	20,463	11,787
Identifiable Assets	565,599				565,889				565,599	565,889	506,156
Long-Lived Assets	323,762				339,601				323,762	339,601	265,905
Forged and Cast Mill Rolls [Member]
Revenue from External Customer [Line Items]
Net sales									254,638	230,531	129,499
Forged Engineered Products [Member]
Revenue from External Customer [Line Items]
Net sales									89,891	17,121	22,768
Heat Exchange Coils [Member]
Revenue from External Customer [Line Items]
Net sales									28,998	28,139	32,745
Centrifugal Pumps [Member]
Revenue from External Customer [Line Items]
Net sales									35,607	36,359	33,120
Air Handling Systems [Member]
Revenue from External Customer [Line Items]
Net sales									23,267	19,716	20,348
U.S. [Member]
Revenue from External Customer [Line Items]
Net sales									236,856	159,531	126,417
(Loss) Income Before Income Taxes and Equity Gains (Losses) in Joint Venture									(18,122)	(25,906)	5,855
Long-Lived Assets	235,646				206,460				235,646	206,460	236,707
Foreign [Member]
Revenue from External Customer [Line Items]
Net sales									195,545	172,335	112,063
(Loss) Income Before Income Taxes and Equity Gains (Losses) in Joint Venture									4,429	(31,614)	(1,335)
Long-Lived Assets	88,116				133,141				88,116	133,141	29,198
Operating Segments [Member]
Revenue from External Customer [Line Items]
Net sales									432,401	331,866	238,480
(Loss) Income Before Income Taxes and Equity Gains (Losses) in Joint Venture									8,601	(37,755)	19,722
Corporate Costs, Including Other Income (Expense) [Member]
Revenue from External Customer [Line Items]
Net sales									0	0	0
(Loss) Income Before Income Taxes and Equity Gains (Losses) in Joint Venture									(22,294)	(19,765)	(15,202)
Capital Expenditures									174	741	305
Depreciation and amortization									191	114	57
Identifiable Assets	19,031				44,541				19,031	44,541	94,414
Forged and Cast Engineered Products [Member] | Operating Segments [Member]
Revenue from External Customer [Line Items]
Net sales									344,529	247,652	152,267
(Loss) Income Before Income Taxes and Equity Gains (Losses) in Joint Venture									(1,826)	(42,878)	(3,444)
Capital Expenditures									14,165	9,440	8,608
Depreciation and amortization									21,124	19,166	10,468
Identifiable Assets	414,227				348,331				414,227	348,331	228,718
Air and Liquid Processing [Member] | Operating Segments [Member]
Revenue from External Customer [Line Items]
Net sales									87,872	84,214	86,213
(Loss) Income Before Income Taxes and Equity Gains (Losses) in Joint Venture									10,427	5,123	23,166
Capital Expenditures									560	385	494
Depreciation and amortization									1,072	1,183	1,262
Identifiable Assets	$ 132,341				$ 173,017				$ 132,341	$ 173,017	$ 183,024