CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net income	$ 240,907	$ 217,997	$ 202,691
Adjustments to reconcile net income to net cash provided from operating activities:
Depreciation and amortization	30,816	25,292	21,950
Accretion of contingent consideration liabilities	995	1,083	967
Stock-based compensation expense	28,437	27,092	25,693
Deferred income taxes	21,344	8,063	24,375
Changes in assets and liabilities:
Accounts receivable	(17,678)	(48,993)	(16,951)
Prepaid expenses and other assets	(244)	(3,433)	3,882
Other assets	1,153	3,932	(3,601)
Accounts payable and accrued expenses	16,953	21,480	(38,918)
Income taxes payable	(7,343)	6,704	18,706
Long-term professional liabilities	9,941	9,843	1,915
Other liabilities	411	1,959	(151)
Net cash provided from operating activities	325,692	271,019	240,558
Cash flows from investing activities:
Acquisition payments, net of cash acquired	(441,006)	(154,885)	(338,596)
Purchases of investments	(33,120)	(42,526)	(26,478)
Proceeds from sales or maturities of investments	28,073	38,170	15,575
Purchases of property and equipment	(14,495)	(31,332)	(12,113)
Net cash used in investing activities	(460,548)	(190,573)	(361,612)
Cash flows from financing activities:
Borrowings on line of credit	517,500	512,500	684,000
Payments on line of credit	(402,500)	(630,000)	(587,500)
Payments for amendment of line of credit	(2,397)	(1,970)
Payments of contingent consideration liabilities	(10,231)	(6,561)	(4,405)
Payments on capital lease obligations	(136)	(463)	(262)
Excess tax benefit from exercises of stock options and vesting of restricted stock	6,494	7,031	3,043
Excess tax benefit related to resolution of income tax matters			3,394
Proceeds from issuance of common stock	28,810	31,362	22,532
Net cash provided from (used in) financing activities	137,540	(88,101)	120,802
Net increase (decrease) in cash and cash equivalents	2,684	(7,655)	(252)
Cash and cash equivalents at beginning of year	18,596	26,251	26,503
Cash and cash equivalents at end of year	21,280	18,596	26,251
Supplemental disclosure of cash flow information:
Interest	2,044	2,569	2,559
Income taxes	129,636	119,261	88,601
Non-cash financing activities:
Equipment financed through capital leases		$ 751

Tax benefit related to resolution of income tax matters involving share-based compensation plans. The tax benefit results from the deduction by the entity on its tax return for an award of stock that exceeds the cumulative compensation cost for common stock or preferred stock recognized for financial reporting. Includes any resulting tax benefit that exceeds the previously recognized deferred tax asset (excess tax benefits).

No definition available.