Incentive Plans - Summary of LFI and Other Similar Deferred Compensation Arrangements (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Deferred Compensation Arrangements [Abstract]
Prepaid Compensation Asset, Beginning Balance	$ 73,278	$ 60,433
Prepaid Compensation Asset, Granted	89,817	92,728
Prepaid Compensation Asset, Settled	0	0
Prepaid Compensation Asset, Forfeited	(4,099)	(2,634)
Prepaid Compensation Asset, Amortization	(82,736)	(76,508)
Prepaid Compensation Asset, Increase (Decrease) in fair value of underlying investments	0	0
Prepaid Compensation Asset, Adjustment for estimated forfeitures	0	0
Prepaid Compensation Asset, Other	(557)	(741)
Prepaid Compensation Asset, Ending Balance	75,703	73,278
Compensation Liability, Beginning Balance	207,306	162,422
Compensation Liability, Granted	89,817	92,728
Compensation Liability, Settled	(96,223)	(55,880)
Compensation Liability, Forfeited	(8,052)	(5,531)
Compensation Liability, Amortization	0	0
Compensation Liability, Increase (Decrease) in fair value of underlying investments	(3,827)	7,326
Compensation Liability, Adjustment for estimated forfeitures	6,780	8,748
Compensation Liability, Other	(2,227)	(2,507)
Compensation Liability, Ending Balance	$ 193,574	$ 207,306