Segment Information (Premium Revenue by Line of Business) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Health plan services premiums	$ 10,377,073	$ 10,459,098	$ 9,878,687
Western Region Operations [Member]
Segment Reporting Information [Line Items]
Health plan services premiums	10,377,100	10,459,100	9,876,300
Commercial Premium Revenue [Member]
Segment Reporting Information [Line Items]
Health plan services premiums	5,175,400	5,705,500	5,945,900
Medicare Premium Revenue [Member]
Segment Reporting Information [Line Items]
Health plan services premiums	2,771,400	2,790,500	2,437,100
Medicaid Premium Revenue [Member]
Segment Reporting Information [Line Items]
Health plan services premiums	2,430,300	1,963,100	1,493,300
Divested Operations and Services [Member]
Segment Reporting Information [Line Items]
Health plan services premiums	$ 0	$ 0	$ 2,400