SEGMENT INFROMATION - Segment Financial Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Total sales	$ 759,982	$ 675,574	$ 723,601	$ 772,031	$ 832,849	$ 809,527	$ 847,028	$ 818,594	$ 2,931,188	$ 3,307,998	$ 3,044,454
Income (loss) from operations	62,800	$ 120,096	$ 133,284	$ 142,181	151,209	$ 152,078	$ 155,860	$ 148,420	458,361	607,567	527,109
Interest expense and other, net									(45,524)	(22,199)	(19,254)
Income (loss) from operations before income taxes									412,837	585,368	507,855
Depreciation and amortization									69,795	64,734	61,261
Capital expenditures									50,216	49,428	47,662
Segment assets	6,581,018				3,229,513				6,581,018	3,229,513	3,303,841
External Customers
Segment Reporting Information [Line Items]
Total sales									2,931,188	3,307,998	3,044,454
Intersegment Sales/(Elimination)
Segment Reporting Information [Line Items]
Total sales									0	0	0
Operating Segments | Freight Segment
Segment Reporting Information [Line Items]
Total sales									1,582,617	2,090,087	1,767,662
Income (loss) from operations									344,455	482,640	402,456
Interest expense and other, net									0	0	0
Income (loss) from operations before income taxes									344,455	482,640	402,456
Depreciation and amortization									36,519	36,834	34,579
Capital expenditures									22,726	24,715	22,913
Segment assets	2,949,668				2,708,724				2,949,668	2,708,724	2,516,645
Operating Segments | Transit Segment
Segment Reporting Information [Line Items]
Total sales									1,397,483	1,264,178	1,320,335
Income (loss) from operations									171,446	150,988	147,821
Interest expense and other, net									0	0	0
Income (loss) from operations before income taxes									171,446	150,988	147,821
Depreciation and amortization									31,545	26,196	24,956
Capital expenditures									20,987	22,996	22,859
Segment assets	6,720,302				2,202,614				6,720,302	2,202,614	2,024,312
Operating Segments | External Customers | Freight Segment
Segment Reporting Information [Line Items]
Total sales									1,543,098	2,054,715	1,731,477
Operating Segments | External Customers | Transit Segment
Segment Reporting Information [Line Items]
Total sales									1,388,090	1,253,283	1,312,977
Operating Segments | Intersegment Sales/(Elimination) | Freight Segment
Segment Reporting Information [Line Items]
Total sales									39,519	35,372	36,185
Operating Segments | Intersegment Sales/(Elimination) | Transit Segment
Segment Reporting Information [Line Items]
Total sales									9,393	10,895	7,358
Corporate Activities and Elimination
Segment Reporting Information [Line Items]
Total sales									(48,912)	(46,267)	(43,543)
Income (loss) from operations									(57,540)	(26,061)	(23,168)
Interest expense and other, net									(45,524)	22,199	(19,254)
Income (loss) from operations before income taxes									(103,064)	(48,260)	(42,422)
Depreciation and amortization									1,731	1,704	1,726
Capital expenditures									6,503	1,717	1,890
Segment assets	$ (3,088,952)				$ (1,681,825)				(3,088,952)	(1,681,825)	(1,237,116)
Corporate Activities and Elimination | External Customers
Segment Reporting Information [Line Items]
Total sales									0	0	0
Corporate Activities and Elimination | Intersegment Sales/(Elimination)
Segment Reporting Information [Line Items]
Total sales									$ (48,912)	$ (46,267)	$ (43,543)