Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net income	$ 26,301	$ 29,729	$ 29,346
Adjustments to reconcile net income to net cash provided by operating activites:
Depreciation and amortization	18,138	11,164	9,916
Equity-based compensation	25,537	21,884	20,444
Bad debt expense	1,628	3,363	2,074
Net deferred income taxes	6,432	4,811	3,050
Other	3,385	3,295	1,606
Changes in assets and liabilities providing/(using) cash, net of acquired balances
Accounts receivable	387	(19,821)	(3,231)
Unbilled services	(1,015)	(14,471)	(12)
Prepaid expenses and other current assets	(2,591)	1,399	(930)
Other assets	(4,339)	(146)	(1,802)
Accounts payable and accrued expenses	4,698	5,527	(1,869)
Accrued compensation and benefits	18,363	4,379	6,157
Deferred revenues	2,069	1,756	(1,378)
Other liabilities	(2,916)	(869)	734
Payments Pursuant to the Tax Receivable Agreement	(6,033)	(5,536)	(4,267)
Net cash provided by operating activities	90,044	46,464	59,838
Cash flows from investing activities:
Purchase of property and equipment	(23,706)	(8,057)	(7,080)
Business acquisitions, net of cash acquired	(13,614)	(53,464)	(18,217)
Purchase of investments	(3,150)	(6,200)	(3,175)
Increase in Restricted Cash	0	(6,400)	0
Net cash used in investing activities	(40,470)	(74,121)	(28,472)
Cash flows from financing activities:
Borrowings under revolving line of credit	35,000	0	0
Repayments of revolving line of credit	(12,500)	0	0
Net proceeds from sale of Class A common stock	49,244	0	(3)
Redemption of noncontrolling unitholders	(58,972)	0	0
Dividends	(13,683)	(9,989)	(6,618)
Repurchases of Class A common stock	(9,284)	(28,891)	(8,897)
Payments of contingent consideration	(6,550)	0	0
Distributions and other payments to noncontrolling unitholders	(4,082)	(8,447)	(9,833)
Payments of Debt Issuance Costs	0	(302)	0
Proceeds from exercises of stock options	16	267	144
Excess tax benefit from equity-based compensation	836	963	(64)
Net cash used in financing activities	(19,975)	(46,399)	(25,271)
Effect of exchange rate on cash and cash equivalents	147	(286)	(78)
Net increase/(decrease) in cash and cash equivalents	29,746	(74,342)	6,017
Cash and cash equivalents at beginning of period	38,986	113,328	107,311
Cash and cash equivalents at end of period	68,732	38,986	113,328
Interest paid	590	102	122
Income taxes paid	16,163	5,503	10,410
Issuance of Class A common stock for acquisitions	$ 3,079	$ 15,487	$ 2,535