Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income	$ 21,187	$ 17,405
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	15,628	14,353
Amortization of capitalized loan fees	201	262
Share-based compensation	5,819	2,816
(Recovery of) provision for doubtful accounts	(7)	1,129
Deferred income taxes	87	(1,268)
Asset impairment charges	2,707	7,774
Other non-cash items	364	130
Changes in operating assets and liabilities:
Billed and unbilled accounts receivable	39,264	(60,833)
Accounts payable and accrued expenses	(20,457)	13,048
Deferred revenue	8,232	(1,058)
Other assets and liabilities	2,673	5,596
Net cash provided by (used in) operating activities	75,698	(646)
Cash flows from investing activities:
Purchases of property and equipment	(10,571)	(4,774)
Net cash used in investing activities	(10,571)	(4,774)
Cash flows from financing activities:
Proceeds from revolving line of credit	15,000	0
Repayments of revolving line of credit	(25,000)	(30,000)
Proceeds from exercise of stock options	5,153	3,559
Payments related to tax withholding for share-based compensation	(1,173)	(11)
Net cash used in financing activities	(6,020)	(26,452)
Effect of exchange rate changes on cash and cash equivalents	2,827	42
Net increase (decrease) in cash and cash equivalents	61,934	(31,830)
Cash and cash equivalents, beginning of period	102,471	85,011
Cash and cash equivalents, end of period	$ 164,405	$ 53,181