SEGMENT INFORMATION (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total net sales									$ 2,391,336,000	$ 2,487,961,000	$ 2,411,835,000
Net Sales	$ 668,444,000	$ 571,614,000	$ 550,047,000	$ 601,231,000	$ 655,771,000	$ 614,880,000	$ 638,996,000	$ 578,314,000	2,391,336,000	2,487,961,000	2,411,835,000
Operating income									288,848,000	403,953,000	373,626,000
Depreciation and amortization									115,903,000	102,412,000	102,949,000
Total assets	4,021,334,000				3,764,261,000				4,021,334,000	3,764,261,000	3,255,385,000
PropertyPlantAndEquipmentAdditions									47,499,000	69,752,000	53,417,000
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating income									326,613,000	439,062,000	409,973,000
Total assets	3,818,305,000				3,459,025,000				3,818,305,000	3,459,025,000	3,079,972,000
Operating Segments [Member] | Commercial/Industrial
Segment Reporting Information [Line Items]
Total net sales									951,292,000	1,138,740,000	1,113,138,000
Operating income									81,581,000	179,637,000	167,647,000
Depreciation and amortization									44,921,000	45,895,000	48,174,000
Total assets	1,315,361,000				1,363,592,000				1,315,361,000	1,363,592,000	1,312,823,000
PropertyPlantAndEquipmentAdditions									21,643,000	28,983,000	26,510,000
Operating Segments [Member] | Defense
Segment Reporting Information [Line Items]
Total net sales									734,041,000	626,282,000	603,794,000
Operating income									140,406,000	137,286,000	140,680,000
Depreciation and amortization									38,507,000	22,204,000	21,537,000
Total assets	1,655,564,000				1,209,706,000				1,655,564,000	1,209,706,000	975,047,000
PropertyPlantAndEquipmentAdditions									4,326,000	8,479,000	9,100,000
Operating Segments [Member] | Power
Segment Reporting Information [Line Items]
Total net sales									708,865,000	726,237,000	697,491,000
Operating income									104,626,000	122,139,000	101,646,000
Depreciation and amortization									28,344,000	30,213,000	29,294,000
Total assets	847,380,000				885,727,000				847,380,000	885,727,000	792,102,000
PropertyPlantAndEquipmentAdditions									18,656,000	28,700,000	11,944,000
Operating Segments [Member] | Corporate And Other [Member]
Segment Reporting Information [Line Items]
Operating income									(37,765,000)	(35,109,000)	(36,347,000)
Depreciation and amortization									4,131,000	4,100,000	3,944,000
Total assets	175,445,000				305,236,000				175,445,000	305,236,000	175,413,000
PropertyPlantAndEquipmentAdditions									2,874,000	3,590,000	5,863,000
Operating Segments [Member] | Assets Held For Sale
Segment Reporting Information [Line Items]
Total assets	$ 27,584,000				$ 0				27,584,000	0	0
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Total net sales									(2,862,000)	(3,298,000)	(2,588,000)
Operating income									$ (37,765,000)	$ (35,109,000)	$ (36,347,000)