Commitments and Contingencies Future minimum lease payments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Future minimum lease payments [Line Items]
Operating Leases, Future Minimum Payments Due	$ 38,322
Operating Leases, Future Minimum Payments, Due in Two Years	39,381
Operating Leases, Future Minimum Payments, Due in Three Years	33,239
Operating Leases, Future Minimum Payments, Due in Four Years	50,630
Operating Leases, Future Minimum Payments, Due in Five Years	26,284
Future minimum lease payments and obligations	165,666
Operating leases [Member]
Future minimum lease payments [Line Items]
Operating Leases, Future Minimum Payments Due	21,257
Operating Leases, Future Minimum Payments, Due in Two Years	19,688
Operating Leases, Future Minimum Payments, Due in Three Years	18,678
Operating Leases, Future Minimum Payments, Due in Four Years	16,870
Operating Leases, Future Minimum Payments, Due in Five Years	16,033
Future minimum lease payments and obligations	62,505
Payments pursuant to the TRA [Member]
Future minimum lease payments [Line Items]
Operating Leases, Future Minimum Payments Due	7,623
Operating Leases, Future Minimum Payments, Due in Two Years	8,985
Operating Leases, Future Minimum Payments, Due in Three Years	9,324
Operating Leases, Future Minimum Payments, Due in Four Years	9,686
Operating Leases, Future Minimum Payments, Due in Five Years	10,080
Future minimum lease payments and obligations	102,383
Revolving Credit Facility [Member]
Future minimum lease payments [Line Items]
Operating Leases, Future Minimum Payments Due	0	[1]
Operating Leases, Future Minimum Payments, Due in Two Years	0	[1]
Operating Leases, Future Minimum Payments, Due in Three Years	0	[1]
Operating Leases, Future Minimum Payments, Due in Four Years	22,500	[1]
Operating Leases, Future Minimum Payments, Due in Five Years	0	[1]
Future minimum lease payments and obligations	0	[1]
Contingent consideration obligations [Member]
Future minimum lease payments [Line Items]
Operating Leases, Future Minimum Payments Due	5,964	[2]
Operating Leases, Future Minimum Payments, Due in Two Years	6,662	[2]
Operating Leases, Future Minimum Payments, Due in Three Years	2,303	[2]
Operating Leases, Future Minimum Payments, Due in Four Years	1,407	[2]
Operating Leases, Future Minimum Payments, Due in Five Years	171	[2]
Future minimum lease payments and obligations	778	[2]
Acquisition retention expenses [Member]
Future minimum lease payments [Line Items]
Operating Leases, Future Minimum Payments Due	3,478	[3]
Operating Leases, Future Minimum Payments, Due in Two Years	4,046	[3]
Operating Leases, Future Minimum Payments, Due in Three Years	2,934	[3]
Operating Leases, Future Minimum Payments, Due in Four Years	167	[3]
Operating Leases, Future Minimum Payments, Due in Five Years	0	[3]
Future minimum lease payments and obligations	$ 0	[3]

[1] (a) Reflects principal payments only. Excludes amounts for interest and unused commitment fees.

[2] (b) Reflects the probability weighted fair market value of acquisition-related contingent consideration payable. The maximum remaining eligible contingent consideration payable totaled $24,765 at December 31, 2012.

[3] (c) Acquisition retention expenses include expense associated with cash-based retention incentives to certain individuals who became employees of the Company through an acquisition. Cash-based incentives are generally subject to certain annual or cliff vesting provisions up to four years contingent upon certain conditions which may include employment. These incentives may be in addition to future grants or cash bonuses awarded as a component of ongoing incentive compensation.