Accumulated Other Comprehensive Income - Components of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance			$ 1,972,677
Other comprehensive loss before reclassifications		$ (565)	(447)	$ (27,510)
Gross amounts reclassified from accumulated other comprehensive income				1,488
Foreign currency translation				0
Other comprehensive income (loss), net of tax	$ 0	(565)	(447)	(26,022)
Gross amounts reclassified within accumulated other comprehensive income		452	329	18,973
Balance	2,083,038		2,083,038
Total Post-Retirement Benefits Adjustments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance		678	2,305	692
Other comprehensive loss before reclassifications		0	(447)	269
Gross amounts reclassified from accumulated other comprehensive income				1,488
Foreign currency translation				518
Other comprehensive income (loss), net of tax		0	(447)	2,275
Gross amounts reclassified within accumulated other comprehensive income		0	0	(2,289)
Balance	1,858	678	1,858	678
Foreign Currency Translation Adjustments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance		(79,362)	(79,927)	(52,148)
Other comprehensive loss before reclassifications		(565)	0	(27,779)
Gross amounts reclassified from accumulated other comprehensive income				0
Other comprehensive income (loss), net of tax		(565)	0	(27,779)
Gross amounts reclassified within accumulated other comprehensive income		0	0	0
Balance	(79,927)	(79,927)	(79,927)	(79,927)
Non-controlling Interest - Principal Equityholders Reclassification [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance		60,838	59,625	40,546
Other comprehensive loss before reclassifications		0	0	0
Gross amounts reclassified from accumulated other comprehensive income				0
Foreign currency translation				(518)
Other comprehensive income (loss), net of tax		0	0	(518)
Gross amounts reclassified within accumulated other comprehensive income		452	329	21,262
Balance	59,954	61,290	59,954	61,290
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance		(17,846)	(17,997)	(10,910)
Other comprehensive income (loss), net of tax			(118)
Balance	$ (18,115)	$ (17,959)	$ (18,115)	$ (17,959)