Income Taxes - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	0 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Taxes Payable	$ 20,304	$ 4,713	$ 20,304
LP Units exchanged by employees (in shares)	983	2,913	2,108
LP Units Exchanged by Employees Which Triggered Additional Liability Under Tax Receivable Agreement		1,377
Payment to the LP Unit holders of the cash tax savings (as a percent)		85.00%
Retained percent of tax benefits (as a percent)		15.00%
Deferred Tax Assets - Non-Current	229,449	251,613	229,449
Amounts Due Pursuant to Tax Receivable Agreements	165,350	175,771	165,350
Increase to Additional Paid-In-Capital		20,222	15,022
Increase (decrease) in deferred tax assets, changes in compensation benefits		5,777
Increase (decrease) in deferred tax assets, changes in depreciation and amortization		5,931
Increase (decrease) in deferred tax assets, changes in unrealized gain (loss) on marketable securities		182	(111)
Increase (decrease) in deferred tax assets, changes in foreign currency translation adjustments		307	1,870
Unrecognized tax benefits that would affect the effective tax rate		474
Income tax penalties and interest expense		166	16
Income tax penalties and interest accrued	49	215	49
Tax benefits associated with the lapse of statute of limitations			(603)
U.K. [Member]
Income Taxes [Line Items]
Net operating loss and tax credit carryforwards		2,398
Exchange of LP Units [Member]
Income Taxes [Line Items]
LP Units exchanged by employees (in shares)		1,930
Deferred Tax Assets - Non-Current		31,534
Amounts Due Pursuant to Tax Receivable Agreements		26,804
Increase to Additional Paid-In-Capital		4,730
Foreign Subsidiaries [Member]
Income Taxes [Line Items]
Undistributed earnings of foreign subsidiaries		4,476
Unrecognized net deferred tax liability		$ 1,288