Condensed Consolidated Statements of Cash Flows (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Cash flows from operating activities:
Net income	$ 79,000	$ 96,040	$ 164,386	$ 183,491
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	7,040	6,724	13,882	13,482
Provision for doubtful accounts	17,487	23,034	30,154	45,799
Deferred income taxes	(4,492)	(6,485)	(7,177)	(9,463)
Excess tax benefit from stock option exercises	(627)	(1,019)	(978)	(1,940)
Stock-based compensation expense	4,758	4,186	8,672	8,999
Other	(987)	334	(2,417)	490
Changes in operating assets and liabilities:
Restricted cash	1,433	5,228	(132)	1,821
Accounts receivable	(4,730)	(33,134)	(8,258)	(58,763)
Accounts payable	(6,681)	7,642	(1,912)	14,841
Other operating assets and liabilities	(32,886)	(20,711)	24,036	22,340
Deferred revenue	1,307	5,312	22,485	25,174
Net cash flows from operating activities	60,622	87,151	242,741	246,271
Cash flows from investing activities:
Facility expenditures and land purchases	(1,173)	(1,754)	(1,675)	(2,593)
Capital expenditures, net	(7,487)	(7,241)	(12,186)	(12,539)
Proceeds from sales and maturities of investments and repayment of notes	118,307	115,128	260,392	199,826
Purchase of investments and note advances	(123,104)	(115,602)	(281,693)	(222,774)
Net cash flows from investing activities	(13,457)	(9,469)	(35,162)	(38,080)
Cash flows from financing activities:
Excess tax benefit from stock option exercises	627	1,019	978	1,940
Proceeds from exercise of stock options	1,955	1,594	4,983	2,620
Repurchase of common stock and shares tendered for taxes	(79,434)	(105,315)	(219,084)	(201,015)
Net cash flows from financing activities	(76,852)	(102,702)	(213,123)	(196,455)
Net change in cash and cash equivalents	(29,687)	(25,020)	(5,544)	11,736
Cash and cash equivalents at beginning of period	187,922	165,544	163,779	128,788
Cash and cash equivalents at end of period	$ 158,235	$ 140,524	$ 158,235	$ 140,524