CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement [Abstract]
Revenues	$ 1,239,705	$ 597,281	$ 438,065
Cost of services	855,382	397,176	288,609
Gross profit	384,323	200,105	149,456
Selling, general and administrative expenses	273,528	153,360	128,715
Amortization of intangible assets	18,016	2,346	2,115
Impairment of goodwill	0	0	15,399
Operating income	92,779	44,399	3,227
Interest expense, net	(17,823)	(2,936)	(8,168)
Income (loss) before income taxes	74,956	41,463	(4,941)
Provision for income taxes	32,303	17,166	4,956
Net income (loss)	42,653	24,297	(9,897)
Earnings (loss) per share:
Basic (in dollars per share)	$ 0.91	$ 0.66	$ (0.27)
Diluted (in dollars per share)	$ 0.89	$ 0.64	$ (0.27)
Number of shares and share equivalents used to calculate earnings (loss) per share:
Basic (in shares)	46,739	36,876	36,429
Diluted (in shares)	47,826	37,758	36,429
Reconciliation of net income to comprehensive income:
Net income (loss)	42,653	24,297	(9,897)
Changes in fair value of derivative, net of income tax of $21 and $227, respectively	(21)	(380)	0
Foreign currency translation adjustment	854	(1,662)	(1,122)
Comprehensive income (loss)	$ 43,486	$ 22,255	$ (11,019)