Accumulated Other Comprehensive Income - Changes in AOCI, net of tax (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, net of tax, beginning of period		$ 686,616	$ 1,484,458	$ 736,657
OCI before reclassifications		355,773	(514,094)	916,952
Amounts reclassified from AOCI		(344,393)	(326,979)	(128,094)
Tax benefit (expense)		17,550	43,231	(41,057)
Net current period OCI - net of tax		28,930	(797,842)	747,801
Balance, net of tax, end of period		715,546	686,616	1,484,458
Cumulative adjustments recorded to value of future policy benefit reserves, amount		(62,295)	(170,688)	400,456
Unrealized Gains (Losses) on Investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, net of tax, beginning of period	[1]	803,094	1,590,114	822,432
OCI before reclassifications	[1]	254,333	(474,304)	954,326
Amounts reclassified from AOCI	[1]	(353,910)	(346,911)	(143,330)
Tax benefit (expense)	[1]	26,912	34,195	(43,314)
Net current period OCI - net of tax	[1]	(72,665)	(787,020)	767,682
Balance, net of tax, end of period	[1]	730,429	803,094	1,590,114
Cumulative adjustments recorded to value of future policy benefit reserves, amount		(62,300)
Cumulative impact of net unrealized gains (losses) on future policy benefit reserve		212,100	274,400
OTTI Losses Recognized in AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, net of tax, beginning of period		(57,502)	(76,047)	(89,190)
OCI before reclassifications		0	0	0
Amounts reclassified from AOCI		6,599	18,987	14,082
Tax benefit (expense)		(49)	(442)	(939)
Net current period OCI - net of tax		6,550	18,545	13,143
Balance, net of tax, end of period		(50,952)	(57,502)	(76,047)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, net of tax, beginning of period		(36,503)	(11,188)	14,541
OCI before reclassifications		102,772	(33,690)	(26,497)
Amounts reclassified from AOCI		0	0	87
Tax benefit (expense)		(7,299)	8,375	681
Net current period OCI - net of tax		95,473	(25,315)	(25,729)
Balance, net of tax, end of period		58,970	(36,503)	(11,188)
Underfunded Pension Liability
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, net of tax, beginning of period		(24,641)	(20,789)	(13,239)
OCI before reclassifications		(1,332)	(6,100)	(10,877)
Amounts reclassified from AOCI		3,100	1,145	812
Tax benefit (expense)		(2,014)	1,103	2,515
Net current period OCI - net of tax		(246)	(3,852)	(7,550)
Balance, net of tax, end of period		(24,887)	(24,641)	(20,789)
Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, net of tax, beginning of period		2,168	2,368	2,113
OCI before reclassifications		0	0	0
Amounts reclassified from AOCI		(182)	(200)	255
Tax benefit (expense)		0	0	0
Net current period OCI - net of tax		(182)	(200)	255
Balance, net of tax, end of period		$ 1,986	$ 2,168	$ 2,368

[1] Included in these amounts is the impact of Shadow Adjustments on future policy benefit reserves. As of December 31, 2015, $274.4 million was recorded. During the year ended December 31, 2016, additional net impacts of $(62.3) million were recorded, resulting in a total cumulative net impact of Shadow Adjustments on future policy benefit reserves of $212.1 million at December 31, 2016.