Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net income	$ 25,857	$ 17,716
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of acquisition-related intangible assets		214
Depreciation & amortization	6,221	4,236
Provision for losses on accounts receivable (Note 1)	5,125	157
Stock-based compensation expense	3,267	3,109
Deferred income taxes	(1,142)	1,080
Loss on disposal of property and equipment	17	1
Changes in operating assets and liabilities:
(Increase) in trade accounts receivable, net	(10,909)	(5,230)
(Increase) in prepaid expenses & other current assets	(1,541)	(3,607)
(Increase) in other assets	(6)	(8)
Increase in accounts payable	2,183	2,725
Increase in accrued expenses	1,303	1,162
Increase (decrease) in other current liabilities	119	(116)
Increase (decrease) in other long-term liabilities	862	(113)
Net cash provided by operating activities	31,356	21,326
Cash flows from investing activities:
Purchases of property and equipment	(3,945)	(11,374)
Capitalized internal use software development costs	(1,079)	(550)
Net cash used in investing activities	(5,024)	(11,924)
Cash flows from financing activities:
Proceeds from employee common stock purchases	904	806
Tax deductions related to stock-based compensation	1,335	1,197
Net cash provided by financing activities	2,239	2,003
Net increase in cash	28,571	11,405
Cash, beginning of period	62,358	61,639
Cash, end of period	90,929	73,044
Non-cash investing activities:
Capital expenditures accrued but not yet paid	5	657
Cash payments:
Income taxes paid	12,744	11,854
Cash dividends on common stock previously restricted for payment of dividend		$ 16,231