Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 149,654	$ 83,533
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Amortization and depreciation	19,304	18,953
Share-based compensation expense	15,700	16,877
Deferred income taxes	3,476	12,748
Excess tax benefit on share-based compensation	(1,354)	(430)
Net realized (gain) loss on investments	(2,236)	(22,936)
Other changes	15,926	15,524
Changes in assets and liabilities, net of effects of acquisitions and dispositions:
Premiums receivable and unearned premiums	(412,141)	(232,780)
Other current assets, receivables and noncurrent assets	(216,808)	27,481
Amounts receivable/payable under government contracts	33,597	29,051
Reserves for claims and other settlements	504,247	(24,887)
Accounts payable and other liabilities	188,343	(57,604)
Net cash provided by (used in) operating activities	297,708	(134,470)
CASH FLOWS FROM INVESTING ACTIVITIES:
Sales of investments	192,250	573,406
Maturities of investments	43,679	51,414
Purchases of investments	(228,437)	(559,442)
Purchases of property and equipment	(29,956)	(26,765)
Sales (purchases) of restricted investments and other	760	(2,589)
Net cash (used in) provided by investing activities	(21,704)	36,024
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options and employee stock purchases	6,472	8,173
Excess tax benefit on share-based compensation	1,354	430
Repurchases of common stock	(12,518)	(77,464)
Borrowings under financing arrangements	0	323,000
Repayment of borrowings under financing arrangements	0	(298,000)
Net increase (decrease) in checks outstanding, net of deposits	0	75,552
Customer funds administered	(101,370)	6,263
Net cash (used in) provided by financing activities	(106,062)	37,954
Net increase (decrease) in cash and cash equivalents	169,942	(60,492)
Cash and cash equivalents, beginning of period	433,155	340,110
Cash and cash equivalents, end of period	603,097	279,618
SUPPLEMENTAL CASH FLOWS DISCLOSURE:
Interest paid	14,754	15,499
Income taxes paid	$ 59,324	$ 34,006