Segment Reporting (Segment Reporting Information) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 segment	Jun. 30, 2013
Segment Reporting [Abstract]
Reportable segments (in number of segments)			4
Revenues:
Revenues	$ 468,618	$ 407,864	$ 907,892	$ 786,908
Gross Profit:
Total Gross Profit	152,727	121,332	290,315	231,443
Operating Income (Loss):
Total Operating Income	38,648	31,775	65,930	54,630
Amortization of Intangible Assets	6,156	5,275	12,328	10,654
Apex
Revenues:
Revenues	297,893	262,347	576,301	502,112
Gross Profit:
Total Gross Profit	84,677	72,912	160,183	136,893
Operating Income (Loss):
Total Operating Income	31,708	24,637	54,492	41,866
Amortization of Intangible Assets	4,089	4,881	8,178	9,762
Oxford
Revenues:
Revenues	126,004	109,153	243,504	211,841
Gross Profit:
Total Gross Profit	53,611	37,122	102,637	71,937
Operating Income (Loss):
Total Operating Income	17,828	15,944	32,112	29,610
Amortization of Intangible Assets	1,362	96	2,732	203
Physician
Revenues:
Revenues	33,657	26,466	65,448	52,768
Gross Profit:
Total Gross Profit	10,298	7,640	19,136	15,123
Operating Income (Loss):
Total Operating Income	2,455	2,213	3,714	4,639
Amortization of Intangible Assets	634	176	1,268	352
Life Sciences Europe
Revenues:
Revenues	11,064	9,898	22,639	20,187
Gross Profit:
Total Gross Profit	4,141	3,658	8,359	7,490
Operating Income (Loss):
Total Operating Income	1,028	448	2,227	981
Amortization of Intangible Assets	71	102	142	262
Corporate Segment
Operating Income (Loss):
Total Operating Income	(14,371)	(11,467)	(26,615)	(22,466)
Amortization of Intangible Assets	$ 0	$ 20	$ 8	$ 75