Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 150,373	$ 116,052
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Amortization and depreciation	28,355	22,722
Gain on sale of discontinued operation	0	116,990
Share-based compensation expense	23,388	23,413
Deferred income taxes	18,321	24,883
Excess tax benefit on share-based compensation	(451)	(6,059)
Net realized (gain) loss on investments	(23,306)	(29,661)
Other changes	23,564	6,832
Changes in assets and liabilities, net of effects of acquisitions and dispositions:
Premiums receivable and unearned premiums	7,800	(173,387)
Other current assets, receivables and noncurrent assets	25,953	(78,203)
Amounts receivable/payable under government contracts	31,064	3,218
Reserves for claims and other settlements	(47,778)	113,985
Accounts payable and other liabilities	(69,558)	47,765
Net cash provided by (used in) operating activities	167,725	(45,430)
CASH FLOWS FROM INVESTING ACTIVITIES:
Sales of investments	653,786	1,132,836
Maturities of investments	72,810	97,815
Purchases of investments	(652,044)	(1,283,227)
Purchases of property and equipment	(42,596)	(55,030)
Net cash received from sale of business	0	248,238
(Purchases) sales of restricted investments and other	(4,697)	6,024
Net cash provided by investing activities	27,259	146,656
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options and employee stock purchases	10,642	16,589
Excess tax benefit on share-based compensation	451	6,059
Repurchases of common stock	(77,569)	(69,330)
Borrowings under financing arrangements	323,000	110,000
Repayment of borrowings under financing arrangements	(323,000)	(122,500)
Net increase (decrease) in checks outstanding, net of deposits	(23,842)	34
Customer funds administered	241,363	40,248
Net cash provided by (used in) financing activities	151,045	(18,900)
Net increase in cash and cash equivalents	346,029	82,326
Cash and cash equivalents, beginning of period	340,110	230,253
Cash and cash equivalents, end of period	686,139	312,579
SUPPLEMENTAL CASH FLOWS DISCLOSURE:
Interest paid	16,741	16,990
Income taxes paid	$ 46,031	$ 5,058