Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities
Net income	$ 16,290	$ 17,807
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization of property and equipment	6,105	7,127
Amortization of other intangible assets	614	615
Loss on asset disposals and impairments of property and equipment	440	391
Deferred income taxes	(343)	(2,155)
Equity in net loss of affiliate	2,387	2,356
Distributions from affiliate	1,000	2,949
Bad debt expense	190	430
Non-cash share-based compensation	2,249	2,168
Changes in operating assets and liabilities
Trade accounts receivable	(1,830)	11,054
Prepaid expenses and other assets	(20)	742
Accounts payable	1,459	(815)
Accrued expenses and other current liabilities	(9,263)	(4,703)
Deferred revenue	1,469	1,057
Noncurrent liabilities	850	1,148
Net cash provided by operating activities	21,597	40,171
Cash flows from investing activities
Additions to property and equipment	(4,096)	(4,936)
Net cash used in investing activities	(4,096)	(4,936)
Cash flows from financing activities
Proceeds from stock option exercises and stock purchase plan	2,119	1,120
Stock repurchases		(17,330)
Dividends paid to stockholders	(2,676)	(2,727)
Excess tax benefits realized from share-based awards	315	132
Net cash used in financing activities	(242)	(18,805)
Effect of exchange rate changes on cash and cash equivalents	7	40
Net change in cash and cash equivalents	17,266	16,470
Cash and cash equivalents at beginning of period	66,469	19,715
Cash and cash equivalents at end of period	$ 83,735	$ 36,185