Incentive Plans - Summary of LFI and Other Similar Deferred Compensation Arrangements (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Deferred Compensation Arrangements [Abstract]
Prepaid Compensation Asset, Beginning Balance	$ 75,703	$ 73,278
Prepaid Compensation Asset, Granted	52,121	89,817
Prepaid Compensation Asset, Settled	0	0
Prepaid Compensation Asset, Forfeited	(2,942)	(4,099)
Prepaid Compensation Asset, Amortization	(73,340)	(82,736)
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	(1,892)	(557)
Prepaid Compensation Asset, Ending Balance	49,650	75,703
Compensation Liability, Beginning Balance	193,574	207,306
Compensation Liability, Granted	52,121	89,817
Compensation Liability, Settled	(77,457)	(96,223)
Compensation Liability, Forfeited	(5,380)	(8,052)
Compensation Liability, Amortization	0	0
Compensation Liability, Increase (Decrease) in fair value of underlying investments	3,318	(3,827)
Compensation Liability, Adjustment for estimated forfeitures	4,671	6,780
Compensation Liability, Other	(459)	(2,227)
Compensation Liability, Ending Balance	$ 170,388	$ 193,574