Business Segment Information (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reconciliation of segment profit to income before income taxes
Segment profit	$ 53,167	$ 44,995	$ 118,114	$ 121,544
Stock compensation expense	(13,795)	(9,550)	(27,696)	(14,022)
Changes in fair value of contingent consideration	(2,567)		(17,536)
Non-controlling interest segment profit (loss)	(350)	(648)	(444)	(1,978)
Depreciation and amortization	(25,022)	(22,480)	(48,518)	(42,709)
Interest expense	(1,653)	(2,004)	(3,279)	(2,840)
Interest income	500	275	966	586
Income before income taxes	$ 10,280	$ 10,588	$ 21,607	$ 60,581