Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 50,050	$ (26,586)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Amortization and depreciation	9,439	7,430
Share-based compensation expense	9,935	12,384
Deferred income taxes	3,579	2,977
Excess tax benefit on share-based compensation	(394)	(5,896)
Net realized (gain) loss on investments	(17,289)	(12,958)
Other changes	8,679	6,163
Changes in assets and liabilities, net of effects of acquisitions and dispositions:
Premiums receivable and unearned premiums	(157,482)	(87,970)
Other current assets, receivables and noncurrent assets	7,427	(25,684)
Amounts receivable/payable under government contracts	25,891	(14,725)
Reserves for claims and other settlements	59,771	84,457
Accounts payable and other liabilities	(27,791)	64,575
Net cash (used in) provided by operating activities	(28,185)	4,167
CASH FLOWS FROM INVESTING ACTIVITIES:
Sales of investments	354,813	650,832
Maturities of investments	30,068	38,958
Purchases of investments	(365,081)	(551,285)
Purchases of property and equipment	(13,690)	(15,373)
Sales (purchases) of restricted investments and other	(1,171)	2,710
Net cash provided by investing activities	4,939	125,842
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options and employee stock purchases	6,957	14,415
Excess tax benefit on share-based compensation	394	5,896
Repurchases of common stock	(77,394)	(19,238)
Borrowings under financing arrangements	90,000	100,000
Repayment of borrowings under financing arrangements	(90,000)	(100,000)
Net increase (decrease) in checks outstanding, net of deposits	(23,816)	0
Customer funds administered	7,330	29,697
Net cash (used in) provided by financing activities	(86,529)	30,770
Net increase (decrease) in cash and cash equivalents	(109,775)	160,779
Cash and cash equivalents, beginning of period	340,110	230,253
Cash and cash equivalents, end of period	230,335	391,032
SUPPLEMENTAL CASH FLOWS DISCLOSURE:
Interest paid	1,312	1,549
Income taxes paid	$ 23	$ 1,825