Segment Reporting (Segment Reporting Information) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 segment	Sep. 30, 2012
Segment Reporting [Abstract]
Reportable segments (in number of segments)			5
Revenues:
Total Revenues	$ 432,171	$ 374,511	$ 1,239,287	$ 797,134
Gross Profit:
Total Gross Profit	130,616	115,631	368,457	252,917
Operating Income (Loss):
Total Operating Income	36,888	31,528	93,460	56,378
Apex
Revenues:
Total Revenues	246,369	202,664	692,543	301,167
Gross Profit:
Total Gross Profit	69,448	56,934	188,963	83,917
Operating Income (Loss):
Total Operating Income	20,021	13,204	46,531	9,556
Oxford
Revenues:
Total Revenues	100,005	88,104	296,741	254,970
Gross Profit:
Total Gross Profit	34,660	31,250	101,316	90,266
Operating Income (Loss):
Total Operating Income	14,084	13,251	39,509	36,007
Life Sciences
Revenues:
Total Revenues	44,124	40,646	126,474	122,506
Gross Profit:
Total Gross Profit	14,306	14,002	41,528	41,649
Operating Income (Loss):
Total Operating Income	2,146	3,020	4,093	8,291
Physician
Revenues:
Total Revenues	26,223	27,479	78,991	76,607
Gross Profit:
Total Gross Profit	7,382	8,370	22,505	23,587
Operating Income (Loss):
Total Operating Income	1,416	3,207	5,497	6,269
Healthcare
Revenues:
Total Revenues	15,450	15,618	44,538	41,884
Gross Profit:
Total Gross Profit	4,820	5,075	14,145	13,498
Operating Income (Loss):
Total Operating Income	$ (779)	$ (1,154)	$ (2,170)	$ (3,745)