Incentive Plans - Summary of Fund Interests and Other Similar Deferred Compensation Arrangements (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Deferred Compensation Arrangements [Abstract]
Prepaid Compensation Asset, Beginning Balance	$ 60,433	$ 47,445
Prepaid Compensation Asset, Granted	92,711	72,182
Prepaid Compensation Asset, Settled
Prepaid Compensation Asset, Forfeited	(9)	(309)
Prepaid Compensation Asset, Amortization	(19,407)	(12,488)
Prepaid Compensation Asset, Increase in fair value of underlying investments
Prepaid Compensation Asset, Adjustment for estimated forfeitures
Prepaid Compensation Asset, Other	116	(106)
Prepaid Compensation Asset, Ending Balance	133,844	106,724
Compensation Liability, Beginning Balance	162,422	97,593
Compensation Liability, Granted	92,711	72,182
Compensation Liability, Settled	(45,450)	(14,832)
Compensation Liability, Forfeited	(2)	(396)
Compensation Liability, Amortization
Compensation Liability, Increase in fair value of underlying investments	2,626	3,725
Compensation Liability, Adjustment for estimated forfeitures	899	648
Compensation Liability, Other	232	(111)
Compensation Liability, Ending Balance	$ 213,438	$ 158,809