Significant Accounting Policies (Health Plan Services Revenue Recognition) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Health Care Organizations [Line Items]
Health plans services premiums	$ 3,261,878,000	$ 2,578,874,000	$ 6,143,223,000	$ 5,210,943,000
Medicare Premium Revenue [Member]
Health Care Organizations [Line Items]
Health plans services premiums	757,200,000	688,600,000	1,512,400,000	1,395,000,000
Medicaid Premium Revenue [Member]
Health Care Organizations [Line Items]
Health plans services premiums	1,121,900,000	591,700,000	1,983,900,000	1,191,900,000
Settlement account balance, beginning						0
Settlement account payment, maximum			264,000,000
Settlement account payment, current balance	9,600,000		9,600,000		62,900,000
Receivable with imputed interest, discount	600,000		600,000		4,400,000
Medicare Risk adjustment [Member] | Medicare Premium Revenue [Member]
Health Care Organizations [Line Items]
Health plans services premiums	4,400,000		20,000,000
Medicaid Retro Rate Adjustment [Member] | Medicaid Premium Revenue [Member]
Health Care Organizations [Line Items]
Health plans services premiums		0		42,200,000
State-sponsored health plans settlement account deficit [Member] | Medicaid Premium Revenue [Member]
Health Care Organizations [Line Items]
Health plans services premiums	$ (40,400,000)	$ 14,600,000	$ (53,300,000)	$ 35,400,000