Schedule II - Condensed Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net income	$ 65,744	$ (7,022)	$ 32,789	$ 50,044	$ 49,755	$ 140,297	$ 143,610	$ 137,245	$ 141,555	$ 470,907	$ 488,907
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Change in unrealized gains on securities, net of taxes of $8,787, $(3,273), and $1,863, respectively									297,639	(267,011)	455,808
Change in other-than-temporary impairment gains, net of taxes of $(0), $(0), and $(0), respectively									4,160	(167)	(2,566)
Change in foreign currency translation, net of taxes of $(45), $(68), and $32, respectively									143,023	88,944	45,649
Amortization of pension and postretirement unrecognized net periodic benefit cost and change in funded status, net of taxes of $(4,082), $26,516, and $(51,301), respectively									(7,604)	49,297	(95,318)
Other comprehensive income (loss)									437,218	(128,937)	403,573
Total comprehensive (loss) income									(295,663)	599,844	85,334
Parent Company
Net income									141,555	470,907	488,907
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Change in unrealized gains on securities, net of taxes of $8,787, $(3,273), and $1,863, respectively									(7,876)	6,078	(3,459)
Change in foreign currency translation, net of taxes of $(45), $(68), and $32, respectively									84	126	(59)
Amortization of pension and postretirement unrecognized net periodic benefit cost and change in funded status, net of taxes of $(4,082), $26,516, and $(51,301), respectively									7,580	(49,244)	95,274
Change in subsidiary other comprehensive income									(437,006)	171,977	(495,329)
Other comprehensive income (loss)									(437,218)	128,937	(403,573)
Total comprehensive (loss) income									$ (295,663)	$ 599,844	$ 85,334