Medicare Part D (Details) (USD $)	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Other current assets		$ 706,493,000	$ 583,141,000
Trade accounts payable and accrued expenses		(2,332,638,000)	(1,624,832,000)
Consumer discounts on brand name prescription drugs		50.00%
Risk Corridor Settlement [Member]
Other current assets		2,840,000	1,563,000
Trade accounts payable and accrued expenses		(623,572,000)	(389,203,000)
Net current liability		(620,732,000)	(387,640,000)
Net payable	380,000,000
CMS Subsidies [Member]
Other current assets		26,691,000	16,211,000
Trade accounts payable and accrued expenses		(406,157,000)	(170,231,000)
Net current liability		(379,466,000)	(154,020,000)
Net payable	$ 98,300,000