Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Assets [Abstract]
Cash and cash equivalents	$ 340,110	$ 230,253
Investments-available-for-sale (amortized cost: 2012-$1,753,931, 2011-$1,528,091)	1,812,512	1,557,997
Premiums receivable, net of allowance for doubtful accounts (2012-$668, 2011-$3,318)	373,269	251,911
Amounts receivable under government contracts	228,316	234,740
Other receivables	113,875	225,004
Deferred taxes	51,086	46,659
Other assets	130,796	117,876
Total current assets	3,049,964	2,664,440
Property and equipment, net	183,793	145,302
Goodwill	565,886	605,886
Other intangible assets, net	17,271	20,699
Deferred taxes	13,583	49,685
Investments-available-for-sale-noncurrent (amortized cost: 2012-$0, 2011-$2,450)	0	2,147
Other noncurrent assets	103,893	119,510
Total Assets	3,934,390	3,607,669
Liabilities and Equity [Abstract]
Reserves for claims and other settlements	1,037,973	912,126
Health care and other costs payable under government contracts	75,649	88,440
Unearned premiums	151,048	176,733
Accounts payable and other liabilities	373,426	240,281
Total current liabilities	1,638,096	1,417,580
Senior notes payable	399,095	398,890
Borrowings under revolving credit facility	100,000	112,500
Other noncurrent liabilities	240,169	235,553
Total Liabilities	2,377,360	2,164,523
Commitments and contingencies
Stockholders' Equity:
Preferred stock ($0.001 par value, 10,000 shares authorized, none issued and outstanding)	0	0
Common stock ($0.001 par value, 350,000 shares authorized; issued 2012-148,727 shares; 2011-146,804 shares )	149	147
Additional paid-in capital	1,329,000	1,278,037
Treasury common stock, at cost (2012-67,426 shares of common stock; 2011-64,847 shares of common stock)	(2,092,625)	(2,023,129)
Retained earnings	2,293,522	2,171,459
Accumulated other comprehensive income	26,984	16,632
Total Stockholders’ Equity	1,557,030	1,443,146
Total Liabilities and Stockholders’ Equity	$ 3,934,390	$ 3,607,669