Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 28,787	$ 50,050
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Amortization and depreciation	9,663	9,439
Share-based compensation expense	9,164	9,935
Deferred income taxes	18,129	3,579
Excess tax benefit on share-based compensation	(997)	(394)
Net realized (gain) loss on investments	(308)	(17,289)
Other changes	9,562	8,679
Changes in assets and liabilities, net of effects of acquisitions and dispositions:
Premiums receivable and unearned premiums	(16,588)	(157,482)
Other current assets, receivables and noncurrent assets	(147,387)	7,427
Amounts receivable/payable under government contracts	34,089	25,891
Reserves for claims and other settlements	167,883	59,771
Accounts payable and other liabilities	199,461	(27,791)
Net cash provided by (used in) operating activities	311,458	(28,185)
CASH FLOWS FROM INVESTING ACTIVITIES:
Sales of investments	66,499	354,813
Maturities of investments	24,469	30,068
Purchases of investments	(125,564)	(365,081)
Purchases of property and equipment	(17,437)	(13,690)
Sales (purchases) of restricted investments and other	3,537	(1,171)
Net cash (used in ) provided by investing activities	(48,496)	4,939
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options and employee stock purchases	3,746	6,957
Excess tax benefit on share-based compensation	997	394
Repurchases of common stock	(11,292)	(77,394)
Borrowings under financing arrangements	0	90,000
Repayment of borrowings under financing arrangements	0	(90,000)
Net increase (decrease) in checks outstanding, net of deposits	713	(23,816)
Customer funds administered	46,743	7,330
Net cash provided by (used in) financing activities	40,907	(86,529)
Net increase (decrease) in cash and cash equivalents	303,869	(109,775)
Cash and cash equivalents, beginning of period	433,155	340,110
Cash and cash equivalents, end of period	737,024	230,335
SUPPLEMENTAL CASH FLOWS DISCLOSURE:
Interest paid	968	1,312
Income taxes paid	$ 338	$ 23