Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income	$ 65,110	$ 114,771
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	23,190	18,422
Loss on disposal or abandonment of property, equipment and software	79	320
Deferred tax benefit	(1,566)	(144)
Compensation expense related to share-based payments	13,685	10,757
Non-cash interest expense	3,164	5,682
Amortization of investment premiums and other	5,825	7,263
Changes in assets and liabilities (decreasing) increasing cash flows from operations:
Premium receivables	(205,673)	(31,616)
Prepaid expenses, provider and other receivables and other current assets	(4,354)	(28,722)
Other long-term assets	(1,737)	(2,106)
Claims payable	113,050	8,833
Accounts payable, accrued expenses, contractual refunds payable and other current liabilities	1,625	10,653
Unearned revenue	92,263	1,146
Other long-term liabilities	(1,545)	(606)
Net cash provided by operating activities	103,116	114,653
Cash flows from investing activities:
Proceeds from sale or call of available-for-sale securities	755,858	464,366
Purchase of available-for-sale securities	(459,620)	(721,853)
Proceeds from redemption of investments on deposit for licensure	30,614	68,374
Purchase of investments on deposit for licensure	(85,072)	(78,606)
Purchase of property, equipment and software	(28,862)	(20,170)
Purchase of contract rights and related assets	(85,168)	0
Net cash provided by (used in) investing activities	127,750	(287,889)
Cash flows from financing activities:
Proceeds from issuance of long-term debt	77,813	0
Issuance costs of long-term debt	(1,061)	0
Repayment of convertible notes principal	(259,880)	0
Net increase in bank overdrafts	12,553	16,262
Customer funds administered	(46)	3,078
Proceeds from exercise of stock options and employee stock purchases	12,492	40,020
Repurchase of common stock shares	0	(79,997)
Tax benefit related to share-based payments	4,782	12,698
Net cash used in financing activities	(153,347)	(7,939)
Net increase (decrease) in cash and cash equivalents	77,519	(181,175)
Cash and cash equivalents at beginning of period	546,811	763,946
Cash and cash equivalents at end of period	624,330	582,771
Supplemental disclosures of non-cash information:
Employee stock relinquished for payment of taxes	(4,337)	(3,621)
Unrealized gain on available-for-sale securities, net of tax	2,004	5,355
Common stock issued upon conversion of the 2.0% Convertible Senior Notes	129,431	0
Common stock received through hedge instruments upon conversion of the 2.0% Convertible Senior Notes	$ (129,431)	$ 0