Segment Reporting (Segment Reporting Information) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) segment	Jun. 30, 2014 USD ($)
Revenues:
Revenues	$ 485,323	$ 434,424	$ 915,368	$ 841,275
Revenue as Percentage of Consolidated Revenue	100.00%	100.00%	100.00%	100.00%
Gross Profit:
Total Gross Profit	$ 158,534	$ 141,905	$ 294,409	$ 270,060
Operating Income (Loss):
Total Operating Income	32,710	36,769	57,781	63,277
Amortization of Intangible Assets	6,957	5,522	$ 11,826	11,060
Reportable segments (in number of segments) | segment			2
Corporate Segment [Member]
Operating Income (Loss):
Total Operating Income	(20,348)	(13,967)	$ (33,933)	(25,848)
Amortization of Intangible Assets	0	0	0	8
Apex
Revenues:
Revenues	338,704	297,893	632,997	576,301
Gross Profit:
Total Gross Profit	97,652	84,677	177,295	160,183
Operating Income (Loss):
Total Operating Income	34,228	31,708	57,139	54,492
Amortization of Intangible Assets	5,384	4,089	8,906	8,178
Oxford
Revenues:
Revenues	146,619	136,531	282,371	264,974
Gross Profit:
Total Gross Profit	60,882	57,228	117,114	109,877
Operating Income (Loss):
Total Operating Income	18,830	19,028	34,575	34,633
Amortization of Intangible Assets	1,573	1,433	2,920	2,874
Physician Segment [Member]
Operating Income (Loss):
Total Operating Income	405		766
Domestic [Member]
Revenues:
Revenues	$ 462,989	$ 414,624	$ 873,745	$ 801,577
Revenue as Percentage of Consolidated Revenue	95.40%	95.40%	95.50%	95.30%
Assignment [Member]
Revenues:
Revenues	$ 456,592	$ 412,953	$ 862,733	$ 800,810
Revenue as Percentage of Consolidated Revenue	94.10%	95.10%	94.20%	95.20%
Direct hire and conversion fees [Member]
Revenues:
Revenues	$ 28,731	$ 21,471	$ 52,635	$ 40,465
Revenue as Percentage of Consolidated Revenue	5.90%	4.90%	5.80%	4.80%