Income Taxes - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	0 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Taxes Payable		$ 2,515	$ 4,713
LP Units exchanged by employees (in shares)	983	1,421	2,913
Tax Savings Distribution Ratio To Unit Holders		85.00%
Retained Ratio Of Tax Savings		15.00%
Amounts Due Pursuant to Tax Receivable Agreements		191,253	175,771
Deferred Tax Assets - Non-Current		265,901	251,613
Adjustments to Additional Paid in Capital		16,254	20,222
Increase (Decrease) In Deferred Tax Assets Associated With Changes In Depreciation And Amortization		5,374
Deferred Tax Liabilities, Net		12,463
Increase (decrease) in deferred tax assets, changes in unrealized gain (loss) on marketable securities		1,072	182
Increase (decrease) in deferred tax assets, changes in foreign currency translation adjustments		5,129	(307)
Tax Credit Carryforward, Amount		5,054
Deferred Tax Assets, Valuation Allowance, Noncurrent		1,605	0
Income tax penalties and interest expense		191	166
Income tax penalties and interest accrued		229	215
Exchange Of Lp Units [Member]
Income Taxes [Line Items]
Amounts Due Pursuant to Tax Receivable Agreements		31,200
Deferred Tax Assets - Non-Current		26,520
Adjustments to Additional Paid in Capital		4,680
Class A LP Units [Member]
Income Taxes [Line Items]
LP Units exchanged by employees (in shares)		1,162
LP Units Exchanged by Employees Which Triggered Additional Liability Under Tax Receivable Agreement		1,162
Subsidiary of Common Parent [Member]
Income Taxes [Line Items]
Undistributed Earnings of Foreign Subsidiaries		4,719
Unrecognized Deferred Tax Liability Not Recognized Attributable To Reinvested Earnings		1,437
Adjustments to Additional Paid in Capital		$ 1,124