Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenues	$ 2,743,200	$ 2,775,000	[1]	$ 2,738,400		$ 2,797,000	[2]	$ 2,837,800	[3]	$ 2,779,600	$ 2,841,300	$ 2,830,400	$ 11,053,743	$ 11,289,092	$ 11,415,436
Net investment income													69,613	82,434	74,161
Administrative services fees and other income													34,791	17,968	11,523
Divested operations and services revenue													0	40,471	34,446
Interest Expense													32,614	33,220	32,131
Depreciation and amortization													38,589	31,146	31,152
Share-based compensation expense													29,930	28,893	27,602
Segment pretax income (loss)	28,000	108,600		52,000	[4]	81,300		8,400		29,400	7,400	(13,600)	269,953	31,650	161,764
Corporate/Other/Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues													0	0	0
Segment pretax income (loss)													(12,000)	(42,000)	(199,400)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues													10,949,400	11,148,200	11,295,300
Operating Segments [Member] | Western Region Operations [Member]
Segment Reporting Information [Line Items]
Revenues													10,377,100	10,459,100	9,876,300
Net investment income													69,600	82,400	74,100
Administrative services fees and other income													34,800	18,000	11,500
Divested operations and services revenue													0	0	0
Interest Expense													32,600	33,200	31,900
Depreciation and amortization													38,600	31,100	31,200
Share-based compensation expense													26,100	24,100	22,600
Segment pretax income (loss)													207,500	29,200	264,900
Operating Segments [Member] | Government Contracts [Member]
Segment Reporting Information [Line Items]
Revenues													572,300	689,100	1,416,600
Net investment income													0	0	0
Administrative services fees and other income													0	0	0
Divested operations and services revenue													0	0	0
Interest Expense													0	0	0
Depreciation and amortization													0	0	0
Share-based compensation expense													3,800	4,200	4,000
Segment pretax income (loss)													74,500	89,900	185,200
Operating Segments [Member] | Divested Operations and Services [Member]
Segment Reporting Information [Line Items]
Revenues													0	0	2,400
Net investment income													0	0	100
Administrative services fees and other income													0	0	0
Divested operations and services revenue													0	40,500	34,500
Interest Expense													0	0	200
Depreciation and amortization													0	0	0
Share-based compensation expense													0	600	1,000
Segment pretax income (loss)													0	(45,400)	(88,900)
Intersegment eliminations [Member]
Segment Reporting Information [Line Items]
Revenues													0	0	0
Intersegment eliminations [Member] | Western Region Operations [Member]
Segment Reporting Information [Line Items]
Revenues													11,100	11,000	11,800
Intersegment eliminations [Member] | Government Contracts [Member]
Segment Reporting Information [Line Items]
Revenues													0	0	0
Intersegment eliminations [Member] | Divested Operations and Services [Member]
Segment Reporting Information [Line Items]
Revenues													0	0	0
Intersegment eliminations [Member] | Corporate/Other/Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues													$ (11,100)	$ (11,000)	$ (11,800)

[1] Includes $32.1 million of Medicaid premium revenue as a result of Medicaid/Medi-Cal retroactive rate adjustments for periods prior to 2013.

[2] Includes $42.2 million of Medicaid premium revenue as a result of Medicaid/Medi-Cal retroactive rate adjustments related to 2011 and 2012.

[3] Includes $31.5 million of premium revenue as a result of Medicaid/Medi-Cal retroactive rate adjustment related to the third quarter of 2012 and prior periods.

[4] Includes a $12.9 million in pretax costs related to continuing efforts to address scale issues.