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 (loss)	$ 122,063	$ 72,120	$ 204,243
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Amortization and depreciation	31,146	31,152	33,400
Impairment charges	0	0	6,000
Adjustment to loss on sale of Northeast health plan subsidiaries	0	(40,815)	(41,959)
Gain on sale of discontinued operation	(114,834)	0	0
Share-based compensation expense	28,893	27,602	33,112
Deferred income taxes	8,924	7,771	37,164
Excess tax benefit on share-based compensation	(6,089)	(1,349)	(571)
Net realized (gain) loss on investments	(36,680)	(33,029)	(23,019)
Other changes	15,158	22,542	(20,013)
Changes in assets and liabilities, net of effects of acquisitions and dispositions:
Premiums receivable and unearned premiums	(212,998)	65,221	12,548
Other current assets, receivables and noncurrent assets	(28,374)	(54,031)	27,590
Amounts receivable/payable under government contracts	(8,989)	32,754	27,404
Reserves for claims and other settlements	164,306	(29,898)	(9,631)
Accounts payable and other liabilities	70,014	3,340	21,770
Net cash provided by operating activities	32,540	103,380	308,038
CASH FLOWS FROM INVESTING ACTIVITIES:
Sales of investments	1,350,003	1,760,336	1,118,957
Maturities of investments	135,394	189,137	199,425
Purchases of investments	(1,678,582)	(1,814,431)	(1,582,851)
Sales of property and equipment	24	0	19
Purchases of property and equipment	(73,101)	(64,260)	(34,791)
Cash divested related to the sale of business	248,238	0	0
Purchase price adjustment on sale of Northeast Health Plans	0	162,101	76,126
(Purchases) sales of restricted investments and other	5,466	(10,656)	22,522
Net cash provided by (used in) investing activities	(12,558)	222,227	(200,593)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options and employee stock purchases	16,941	13,356	3,644
Excess tax benefit on share-based compensation	6,089	1,349	571
Repurchases of common stock	(69,496)	(389,850)	(236,847)
Borrowings under financing arrangements	110,000	978,500	100,000
Repayments of borrowings under financing arrangements	(122,500)	(872,212)	(316,771)
Net (decrease) increase in checks outstanding, net of deposits	23,842	(46,718)	45,909
Customer funds administered	124,999	(129,917)	(36,616)
Net cash (used in) provided by financing activities	89,875	(445,492)	(440,110)
Net (decrease) increase in cash and cash equivalents	109,857	(119,885)	(332,665)
Cash and cash equivalents, beginning of year	230,253	350,138	682,803
Cash and cash equivalents, end of year	340,110	230,253	350,138
SUPPLEMENTAL CASH FLOWS DISCLOSURE:
Interest paid	31,134	31,332	31,074
Income taxes paid	5,001	55,882	96,319
SUPPLEMENTAL SCHEDULE OF NON-CASH INVESTING AND FINANCING ACTIVITIES: [Abstract]
Accretion of deferred revenues into earnings	12,000	2,738	47,273
Amortization of dscounts into earnings	$ 0	$ 10,429	$ 22,037