Regulatory Requirements (Details) - USD ($)	3 Months Ended																12 Months Ended
	Dec. 31, 2015		Sep. 30, 2015	[3],[4]	Jun. 30, 2015	[5],[6]	Mar. 31, 2015	[7],[8]	Dec. 31, 2014		Sep. 30, 2014	[11],[12]	Jun. 30, 2014	[13],[14]	Mar. 31, 2014	[15]	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Regulatory Assets [Line Items]
Statutory-basis capital and surplus of our regulated subsidiaries	$ 1,800,000,000																$ 1,800,000,000
GAAP net income	37,100,000	[1],[2]	$ 60,300,000		$ 58,400,000		$ 30,000,000		$ 4,900,000	[9],[10]	$ (8,900,000)		$ 120,900,000		$ 28,800,000		185,677,000	$ 145,629,000	$ 170,126,000
Statutory capital and surplus, regulatory requirements	467,300,000																467,300,000
Capital and surplus unavailable for payment of dividends	467,300,000																467,300,000
Restricted net assets	135,800,000																135,800,000
Health Plan Subsidiaries [Member]
Regulatory Assets [Line Items]
Statutory-basis capital and surplus of our regulated subsidiaries	184,300,000								188,500,000								184,300,000	188,500,000
Statutory-basis net income of health plan subsidiaries																	(75,300,000.0)	(130,500,000.0)	(158,000)
Subsidiaries [Member] | Department of Managed Health Care [Member]
Regulatory Assets [Line Items]
GAAP equity	$ 1,600,000,000								$ 1,300,000,000								1,600,000,000	1,300,000,000
GAAP net income																	$ 343,700,000	$ 202,300,000	$ 140,700,000

[1] Includes $22.7 million in pretax expenses primarily related to the Cognizant Transaction.

[2] Includes $58.2 million amortization of deferred costs of health insurer's fee and $21.1 million in other ACA fees.

[3] Includes $21.7 million in pretax expenses primarily related to the Cognizant Transaction.

[4] Includes $58.4 million amortization of deferred costs of health insurer's fee and $22.2 million in other ACA fees.

[5] Includes $26.4 million in pretax expenses primarily related to the Cognizant Transaction.

[6] Includes $58.5 million amortization of deferred costs of health insurer's fee and $21.5 million in other ACA fees.

[7] Includes $1.9 million pretax asset impairment and $44.3 million in pretax expenses primarily related to the Cognizant Transaction.

[8] Includes $57.8 million amortization of deferred costs of health insurer's fee and $20.8 million in other ACA fees.

[9] Includes $3.8 million pretax asset impairment primarily related to our assets held for sale in connection with the Cognizant Transaction and $68.3 million in pretax expenses primarily related to the Cognizant Transaction.

[10] Includes $35.4 million amortization of deferred costs of health insurer's fee and $25.8 million in other ACA fees.

[11] Includes $31.9 million amortization of deferred costs of health insurer's fee and $26.6 million in other ACA fees.

[12] Includes $84.7 million pretax asset impairment related to our assets held for sale in connection with the Cognizant Transaction and $21.1 million in pretax expenses primarily related to the Cognizant transaction.

[13] Includes $37.8 million amortization of deferred costs of health insurer's fee and $22.5 million in other ACA fees.

[14] Includes tax benefit of $72.6 million, net of adjustments, as a result of a loss on the stock of one of our subsidiaries.

[15] Includes $36.3 million amortization of deferred costs of health insurer's fee and $22.5 million in other ACA fees.