Significant Accounting Policies (Accounting for Certain Provisions of the ACA) (Details) (USD $)	3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended		12 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 ACA Health Insurer Fee [Member]	Jun. 30, 2014 ACA Health Insurer Fee [Member]	Jun. 30, 2014 ACA Reinsurance Recovery [Member]	Jun. 30, 2014 ACA Reinsurance Recovery [Member]	Jun. 30, 2014 ACA Risk Adjustment [Member]	Jun. 30, 2014 ACA Risk Adjustment [Member]	Jun. 30, 2014 ACA Risk Corridor [Member]	Jun. 30, 2014 ACA Risk Corridor [Member]	Jun. 30, 2014 ACA 1202, Model 1 [Member]	Mar. 31, 2014 ACA 1202, Model 2 [Member]	Dec. 31, 2013 ACA 1202, Model 2 [Member]	Jun. 30, 2014 Medicaid Premium Revenue [Member]	Jun. 30, 2013 Medicaid Premium Revenue [Member]	Jun. 30, 2014 Medicaid Premium Revenue [Member]	Jun. 30, 2013 Medicaid Premium Revenue [Member]	Jun. 30, 2014 CALIFORNIA Medicaid Premium Revenue [Member] Customers	Jun. 30, 2014 ARIZONA Medicaid Premium Revenue [Member] Customers
Supplementary Insurance Information, by Segment [Line Items]
Accounts payable and other liabilities	$ 496,349,000		$ 496,349,000		$ 397,036,000	$ 148,000,000	$ 148,000,000			$ 30,100,000	$ 30,100,000
Deferred cost, amortization expense						37,800,000	74,100,000
Other assets	259,878,000		259,878,000		132,683,000	74,100,000	74,100,000
Other noncurrent assets	139,205,000		139,205,000		162,551,000							27,300,000	27,300,000
Number of Customers																					1,400,000	45,000
Other receivables	183,795,000		183,795,000		68,919,000			110,600,000	110,600,000
Health plans services premiums	3,261,878,000	2,578,874,000	6,143,223,000	5,210,943,000						(30,100,000)	(30,100,000)	18,600,000	27,300,000	154,700,000	0	4,400,000	1,121,900,000	591,700,000	1,983,900,000	1,191,900,000
Health plan services expenses	2,763,179,000	2,191,918,000	5,165,521,000	4,460,654,000				(77,500,000)	(110,600,000)					144,000,000	0	0
General and administrative expenses	344,734,000	291,437,000	705,757,000	536,672,000										0	0	4,400,000
Administrative services fees and other income	(6,612,000)	2,472,000	(4,214,000)	3,377,000										(7,900,000)	1,400,000	6,500,000
Pretax income	$ 98,802,000	$ 52,028,000	$ 160,762,000	$ 133,331,000										$ 2,800,000	$ 1,400,000	$ 6,500,000