Summary of Significant Accounting Policies (Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Significant Accounting Policies [Line Items]
Health plan services premiums	$ 15,553,348	$ 13,361,170	$ 10,377,073
State Required Premium Income Taxes [Member]
Significant Accounting Policies [Line Items]
Premium taxes paid based on membership or billed premiums	266,500	191,200	124,400
Reinstated Medicaid premium tax [Member]
Significant Accounting Policies [Line Items]
Taxes, Other	222,400	157,100	92,800
Reinstated prior year Medicaid premium taxes [Member] [Member]
Significant Accounting Policies [Line Items]
Taxes, Other			20,200
Medicaid Premium Revenue [Member]
Significant Accounting Policies [Line Items]
Health plan services premiums	6,429,600	4,755,900	2,430,300
Medicaid Premium Revenue [Member] | Reinstated Medicaid premium tax [Member]
Significant Accounting Policies [Line Items]
Health plan services premiums	$ 222,400	$ 157,100	$ 92,800