Significant Accounting Policies (Health Plan Services Revenue Recognition) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Jan. 01, 2013
Health Care Organizations [Line Items]
Accounts payable and other liabilities	$ 1,168,014,000		$ 1,168,014,000		$ 880,374,000
Other noncurrent liabilities	346,915,000		346,915,000		242,705,000
Other noncurrent assets	300,572,000		300,572,000		187,630,000
Health plan services premiums	4,003,432,000	$ 3,261,878,000	7,724,232,000	$ 6,143,223,000
Commercial Premium Revenue [Member]
Health Care Organizations [Line Items]
Health plan services premiums	1,412,900,000	1,377,500,000	2,745,900,000	2,641,600,000
Medicare Premium Revenue [Member]
Health Care Organizations [Line Items]
Health plan services premiums	782,400,000	757,200,000	1,551,300,000	1,512,400,000
Medicaid Premium Revenue [Member]
Health Care Organizations [Line Items]
Health plan services premiums	1,673,100,000	1,121,900,000	3,144,400,000	1,983,900,000
Settlement account balance, beginning						$ 0
Settlement account payment, maximum			264,000,000
State Settlement Account Surplus	171,600,000		171,600,000		53,400,000
Medicare Risk adjustment [Member] | Medicare Premium Revenue [Member]
Health Care Organizations [Line Items]
Health plan services premiums	9,100,000	4,400,000	3,700,000	20,000,000
Medicaid Retro Premium Adjustment [Member] | Medicaid Premium Revenue [Member]
Health Care Organizations [Line Items]
Health plan services premiums	2,600,000		29,800,000
State-sponsored health plans settlement account deficit [Member] | Medicaid Premium Revenue [Member]
Health Care Organizations [Line Items]
Other noncurrent liabilities	0		0
Other noncurrent assets	0		$ 0		0
Health plan services premiums		(40,400,000)		(53,300,000)
Minimum [Member] | Medicaid Premium Revenue [Member]
Health Care Organizations [Line Items]
MLR Rebate Threshold			85.00%
Maximum [Member] | Medicaid Premium Revenue [Member]
Health Care Organizations [Line Items]
MLR Rebate Threshold			95.00%
MLR Rebate, Premium Refund [Member] | Commercial Premium Revenue [Member]
Health Care Organizations [Line Items]
Health plan services premiums	0	0	$ 0	0
MLR Rebate, Premium Refund [Member] | Medicaid Premium Revenue [Member]
Health Care Organizations [Line Items]
Accounts payable and other liabilities	261,500,000		261,500,000		200,600,000
Health plan services premiums	2,500,000	0	(60,900,000)	0
Profit sharing, premium refund [Member] | Medicaid Premium Revenue [Member]
Health Care Organizations [Line Items]
Accounts payable and other liabilities	7,200,000		7,200,000		27,000,000
Other noncurrent liabilities	7,100,000		7,100,000		0
Profit Corridor Payment			36,200,000
Other noncurrent assets	0		0		$ 2,300,000
Health plan services premiums	$ (10,000,000)	$ (6,600,000)	$ (25,800,000)	$ (8,000,000)