Incentive Plans - Summary of LFI and Other Similar Deferred Compensation Arrangements (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
Deferred Compensation Arrangement With Individual Excluding Share Based Payments And Postretirement Benefits [Line Items]
Compensation Liability, Beginning Balance	$ 188,962
Compensation Liability, Ending Balance	228,116
LFI and Other Similar Deferred Compensation Arrangements [Member]
Deferred Compensation Arrangement With Individual Excluding Share Based Payments And Postretirement Benefits [Line Items]
Prepaid Compensation Asset, Beginning Balance	76,362
Prepaid Compensation Asset, Granted	101,552
Prepaid Compensation Asset, Forfeited	(1,571)
Prepaid Compensation Asset, Amortization	(83,301)
Prepaid Compensation Asset, Other	(990)
Prepaid Compensation Asset, Ending Balance	92,052
Compensation Liability, Beginning Balance	188,022
Compensation Liability, Granted	101,529
Compensation Liability, Settled	(89,140)
Compensation Liability, Forfeited	(3,107)
Compensation Liability, Increase (decrease) in fair value of underlying investments	22,118
Compensation Liability, Adjustment for estimated forfeitures	3,704
Compensation Liability, Other	(1,100)
Compensation Liability, Ending Balance	$ 222,026