BUSINESS SEGMENT INFORMATION - Reconciliation of Segment Operating Income to Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended									6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	[1]	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting [Abstract]
Income (loss) from operations	$ 22,641	$ 8,753	$ (883)	$ 7,619	$ (121,618)		$ (20,854)	$ (8,797)	$ 5,573	$ 6,736	$ (3,221)	$ 15,489	$ (24,075)	$ 38,130	$ (145,696)	$ (48,664)
Interest expense		(30,882)	(30,860)	(28,927)			(25,865)	(24,850)	(23,999)	(59,787)	(48,849)	(90,669)	(74,714)	(121,819)	(101,311)	(82,320)
Loss on extinguishment of debt		0					(5,385)					0	(5,385)	0	(5,385)	(49,154)
Interest income		1,374	2,356	1,791			1,555	2,567	2,140	4,147	4,707	5,521	6,262	7,435	7,993	6,400
Gain (loss) on foreign exchange		220	(364)	(1,387)			1,679	(1,313)	2,109	(1,751)	795	(1,531)	2,474	(715)	3,674	(4,016)
Other income		303	254	(122)			356	534	193	132	726	435	1,082	38	1,740	1,031
Loss before income taxes		$ (20,232)	$ (29,497)	$ (21,026)			$ (48,514)	$ (31,859)	$ (13,984)	$ (50,523)	$ (45,842)	$ (70,755)	$ (94,356)	$ (76,931)	$ (238,985)	$ (176,723)

[1] Operating loss for the three months ended December 31, 2015 includes $136.2 million of impairment charges at ROVA and the Coal Valley mine in the Coal - Canada segment.