Condensed Consolidated Statements of Cash Flows - Unaudited (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 14,898	$ 11,806
Adjustments to reconcile net income to net cash provided by operating activities-
Depreciation	5,000	5,837
Amortization	9,736	10,302
Amortization of original issue discount	1,299	1,203
(Gain) loss on short-term investments and other	863	(8)
Deferred income taxes	6,447	(3,111)
Excess tax benefit of stock-based compensation awards	(537)	(286)
Stock-based employee compensation	3,610	3,147
Changes in operating assets and liabilities:
Trade accounts and other receivables, net	10,229	13,252
Other current and non-current assets	(808)	(1,152)
Income taxes payable/receivable	(8,641)	14,614
Trade accounts payable and accrued liabilities	(29,450)	(14,045)
Deferred revenue	9,894	6,630
Net cash provided by operating activities	22,540	48,189
Cash flows from investing activities:
Purchases of property and equipment	(4,492)	(2,318)
Purchases of short-term investments	(23,178)	(10,142)
Proceeds from sale/maturity of short-term investments	29,500	12,100
Acquisition of and investments in client contracts	(407)	(1,693)
Net cash provided by (used in) investing activities	1,423	(2,053)
Cash flows from financing activities:
Proceeds from issuance of common stock	610	556
Repurchase of common stock	(11,343)	(8,078)
Payments on acquired equipment financing		(417)
Payments on long-term debt	(3,750)	(7,000)
Excess tax benefit of stock-based compensation awards	537	286
Net cash used in financing activities	(13,946)	(14,653)
Effect of exchange rate fluctuations on cash	(332)	192
Net increase in cash and cash equivalents	9,685	31,675
Cash and cash equivalents, beginning of period	136,473	146,733
Cash and cash equivalents, end of period	146,158	178,408
Net cash paid during the period for-
Interest	3,378	4,473
Income taxes	$ 611	$ 242