Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010
Operating activities:
Net income	$ 32,750		$ 20,219
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	15,734		15,283
Share-based compensation	4,457		4,887
Gain on disposal of property and equipment	(76)		(648)
Provision for loss on receivables	17		202
Provision for revenue adjustments	1,480		1,462
Deferred income taxes	6,079		(1,624)
Tax benefit for stock options exercised	(232)		(28)
Changes in operating assets and liabilities
Accounts receivable	(8,308)		(8,382)
Prepaid expenses and other current assets	(1,828)		(1,029)
Accounts payable and accrued expenses	4,757		7,519
Net cash provided by operating activities	54,830		37,861
Investing activities:
Proceeds from disposal of property and equipment	997		1,413
Purchases of property and equipment	(20,292)		(11,889)
Other	316		0
Net cash used in investing activities	(18,979)		(10,476)
Financing activities:
Payments of debt and capital lease obligations	(488)		(722)
Proceeds from exercise of stock options	7,721		490
Payments of cash dividends	(6,187)		(6,088)
Repurchase of common stock	(24,294)		0
Common stock issued under employee stock purchase plan	128		91
Tax benefit for stock options exercised	232		28
Net cash used in financing activities	(22,888)		(6,201)
Net increase in cash	12,963		21,184
Cash at beginning of period	74,504	[1]	42,035
Cash at end of period	$ 87,467		$ 63,219

[1] Taken from audited financial statements, which are not presented in their entirety.