Accumulated Other Comprehensive Income (Loss) - Changes in AOCI, net of tax (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax		$ 1,094,557	$ 1,705,170	$ 686,616	$ 1,484,458
OCI before Reclassifications		464,638	(581,964)	1,023,195	(294,319)
Amounts reclassified from AOCI		(110,615)	(85,884)	(225,457)	(150,633)
Tax benefit (expense)		(39,993)	38,852	(75,767)	36,668
Comprehensive income (loss)		314,030	(628,996)	721,971	(408,284)
Ending balance, net of tax		1,408,587	1,076,174	1,408,587	1,076,174
Change in adjustments related to future policy benefit reserves, net of tax		(8,727)	(26,328)	(25,762)	(86,684)
Unrealized gains (losses) on investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	[1]	1,226,295	1,763,795	803,094	1,590,114
OCI before Reclassifications	[1]	392,620	(544,273)	967,642	(290,007)
Amounts reclassified from AOCI	[1]	(112,377)	(87,558)	(229,491)	(162,338)
Tax benefit (expense)	[1]	(31,460)	37,000	(66,167)	31,195
Comprehensive income (loss)	[1]	248,783	(594,831)	671,984	(421,150)
Ending balance, net of tax	[1]	1,475,078	1,168,964	1,475,078	1,168,964
Cumulative impact of net unrealized gains losses on future policy benefit reserve		248,700		248,700		$ 274,400
Change in adjustments related to future policy benefit reserves, net of tax				(25,800)
OTTI losses recognized in AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax		(55,235)	(66,189)	(57,502)	(76,047)
OCI before Reclassifications		0	0	0	0
Amounts reclassified from AOCI		1,810	1,662	4,121	11,598
Tax benefit (expense)		42	(87)	(2)	(165)
Comprehensive income (loss)		1,852	1,575	4,119	11,433
Ending balance, net of tax		(53,383)	(64,614)	(53,383)	(64,614)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax		(52,942)	24,915	(36,503)	(11,188)
OCI before Reclassifications		71,918	(36,362)	56,502	(3,958)
Amounts reclassified from AOCI		0	0	0	0
Tax benefit (expense)		(8,575)	1,939	(9,598)	5,638
Comprehensive income (loss)		63,343	(34,423)	46,904	1,680
Ending balance, net of tax		10,401	(9,508)	10,401	(9,508)
Underfunded pension liability
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax		(25,690)	(19,814)	(24,641)	(20,789)
OCI before Reclassifications		100	(1,329)	(949)	(354)
Amounts reclassified from AOCI		0	0	0	0
Tax benefit (expense)		0	0	0	0
Comprehensive income (loss)		100	(1,329)	(949)	(354)
Ending balance, net of tax		(25,590)	(21,143)	(25,590)	(21,143)
Cash flow hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax		2,129	2,463	2,168	2,368
OCI before Reclassifications		0	0	0	0
Amounts reclassified from AOCI		(48)	12	(87)	107
Tax benefit (expense)		0	0	0	0
Comprehensive income (loss)		(48)	12	(87)	107
Ending balance, net of tax		$ 2,081	$ 2,475	$ 2,081	$ 2,475

[1] . As of December 31, 2015, the cumulative impact of the Shadow Adjustments was $274.4 million. During the six months ended June 30, 2016, net movements of $(25.8) million were recorded, resulting in a total cumulative net impact of Shadow Adjustments on future policy benefit reserves of $248.7 million as of June 30, 2016.