CONSOLIDATED STATEMENT OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating activities:
Net income	$ 28,904	$ 30,530
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	44,315	40,840
Stock-based compensation expense	8,749	10,194
Excess tax benefit from exercised stock options	(5,154)	(11,859)
Deferred income taxes	(6,178)	(5,772)
Increase in allowance for doubtful debts	5,876	2,174
Change in fair value of contingent consideration	23	(2,300)
Loss on disposal of fixed assets	186	62
Changes in operating assets and liabilities:
Accounts receivable	(20,873)	(16,136)
Prepaid expenses	1,175	(4,926)
Prepaid income taxes	4,160	4,810
Other current assets	(89)	550
Other assets	16	(88)
Accounts payable, accrued expenses and other liabilities	8,397	(4,862)
Estimated liability for appeals	5,697	10,613
Net cash provided by operating activities	75,204	53,830
Investing activities:
Proceeds from redemption of certificate of deposit		4,809
Purchase of short-term investments	(21,460)
Purchases of property and equipment	(18,272)	(18,541)
Investment in common stock	(500)	(3,024)
Acquisitions, net		(1,605)
Investment in capitalized software	(2,951)	(1,559)
Net cash used in investing activities	(43,183)	(19,920)
Financing activities:
Financing related to revolving debt	(7,619)
Repayment of term loan		(13,125)
Repayment of revolving debt	(60,000)
Purchases of treasury stock		(10,617)
Payments on contingent consideration		(250)
Payments on capital lease obligations	(1,291)	(692)
Proceeds from exercise of stock options	7,381	10,991
Payments of tax withholdings on behalf of employees for net-share settlement for stock-based compensation	(1,498)	(1,127)
Excess tax benefit from exercised stock options	5,154	11,859
Net cash used in financing activities	(57,873)	(2,961)
Net (decrease)/increase in cash and cash equivalents	(25,852)	30,949
Cash and cash equivalents at beginning of period	135,227	97,003
Cash and cash equivalents at end of period	109,375	127,952
Supplemental disclosure of cash flow information:
Cash paid for income taxes	24,090	20,145
Cash paid for interest	7,666	10,093
Supplemental disclosure of noncash investing activities:
Accrued property and equipment purchases	1,040	267
Equipment purchased through capital leases	$ 2,401	$ 1,693