Segment Information (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 segments	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Reportable segments									3
Revenue from external sources									$ 11,148,200,000	$ 11,295,300,000	$ 12,837,000,000
Intersegment revenues									0	0	0
Net investment income									82,434,000	74,161,000	71,181,000
Administrative service fees and other income									17,968,000	11,523,000	21,126,000
Divested operations and services revenue									40,471,000	34,446,000	186,167,000
Interest Expense									33,220,000	32,131,000	34,880,000
Depreciation and amortization									31,146,000	31,152,000	33,400,000
Share-based compensation expense									28,893,000	27,602,000	33,112,000
Segment pretax income (loss)	8,400,000	29,400,000	7,400,000	(13,600,000)	63,500,000	92,900,000	86,200,000	(80,800,000)	31,650,000	161,764,000	280,612,000
Western Region Operations [Member]
Segment Reporting Information [Line Items]
Revenue from external sources									10,459,100,000	9,876,300,000	9,421,300,000
Intersegment revenues									11,000,000	11,800,000	54,200,000
Net investment income									82,400,000	74,100,000	70,300,000
Administrative service fees and other income									18,000,000	11,500,000	26,600,000
Divested operations and services revenue									0	0	0
Interest Expense									33,200,000	31,900,000	34,900,000
Depreciation and amortization									31,100,000	31,200,000	33,200,000
Share-based compensation expense									24,100,000	22,600,000	26,000,000
Segment pretax income (loss)									29,200,000	264,900,000	210,100,000
Government Contracts [Member]
Segment Reporting Information [Line Items]
Revenue from external sources									689,100,000	1,416,600,000	3,344,500,000
Intersegment revenues									0	0	100,000
Net investment income									0	0	0
Administrative service 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									4,200,000	4,000,000	4,100,000
Segment pretax income (loss)									89,900,000	185,200,000	178,800,000
Divested Operations and Services [Member]
Segment Reporting Information [Line Items]
Revenue from external sources									0	2,400,000	71,200,000
Intersegment revenues									0	0	0
Net investment income									0	100,000	900,000
Administrative service fees and other income									0	0	0
Divested operations and services revenue									40,500,000	34,500,000	186,200,000
Interest Expense									0	200,000	0
Depreciation and amortization									0	0	200,000
Share-based compensation expense									600,000	1,000,000	3,000,000
Segment pretax income (loss)									(45,400,000)	(88,900,000)	(84,600,000)
Corporate/Other/Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from external sources									0	0	0
Intersegment revenues									(11,000,000)	(11,800,000)	(54,300,000)
Net investment income									0	0	0
Administrative service fees and other income									0	0	(5,500,000)
Divested operations and services revenue									0	0	0
Interest Expense									0	0	0
Depreciation and amortization									0	0	0
Share-based compensation expense									0	0	0
Segment pretax income (loss)									$ (42,000,000)	$ (199,400,000)	$ (23,700,000)