Schedule I - Condensed Financial Information of Registrant (Condensed Statements of Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended														12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net income	$ 4,900	[1],[2]	$ (8,900)	[3],[4]	$ 120,900	[5],[6]	$ 28,800	$ 19,800	$ 66,800	[7]	$ 33,500	[8]	$ 50,100	[9]	$ 145,629	$ 170,126	$ 122,063
Unrealized gains (losses) on investments available-for-sale:
Unrealized holding gains (losses) arising during the period															59,073	(78,217)	65,462
Less: Reclassification adjustments for gains included in earnings															(2,710)	(23,975)	(36,680)
Unrealized gains on investments available-for-sale, net															56,363	(102,192)	28,782
Defined benefit pension plans:
Prior service cost arising during the period															0	607	0
Net (loss) gain arising during the period															(11,893)	7,294	(646)
Less: Amortization of prior service cost and net loss included in net periodic pension cost															600	2,572	4,152
Defined benefit pension plans, net															(11,293)	10,473	3,506
Other comprehensive income (loss), before tax															45,070	(91,719)	32,288
Income tax expense (benefit) related to components of other comprehensive income															15,464	(31,868)	21,936
Other comprehensive income, net of tax															29,606	(59,851)	10,352
Comprehensive income															175,235	110,275	132,415
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income															145,629	170,126	122,063
Unrealized gains (losses) on investments available-for-sale:
Unrealized holding gains (losses) arising during the period															59,073	(78,217)	65,462
Less: Reclassification adjustments for gains included in earnings															(2,710)	(23,975)	(36,680)
Unrealized gains on investments available-for-sale, net															56,363	(102,192)	28,782
Defined benefit pension plans:
Prior service cost arising during the period															0	607	0
Net (loss) gain arising during the period															(11,893)	7,294	(646)
Less: Amortization of prior service cost and net loss included in net periodic pension cost															600	2,572	4,152
Defined benefit pension plans, net															(11,293)	10,473	3,506
Other comprehensive income (loss), before tax															45,070	(91,719)	32,288
Income tax expense (benefit) related to components of other comprehensive income															15,464	(31,868)	21,936
Other comprehensive income, net of tax															29,606	(59,851)	10,352
Comprehensive income															$ 175,235	$ 110,275	$ 132,415

[1] 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.

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

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

[4] 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.

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

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

[7] Includes $32.1 million of Medicaid premium revenue as a result of Medicaid/Medi-Cal retroactive rate adjustments for periods prior to 2013.

[8] Includes a $12.9 million in pretax costs related to continuing efforts to address scale issues.

[9] Includes $42.2 million of Medicaid premium revenue as a result of Medicaid/Medi-Cal retroactive rate adjustments related to 2011 and 2012.