Accumulated Other Comprehensive Income (Loss) - Changes in AOCI, net of tax (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax		$ 715,546	$ 686,616
OCI before reclassifications		188,822	558,557
Amounts reclassified from AOCI		(51,147)	(114,842)
Tax benefit (expense)		(8,247)	(35,774)
Comprehensive income (loss)		129,428	407,941
Ending balance, net of tax		844,974	1,094,557
Change in adjustments related to future policy benefit reserves, net of tax		(5,132)	(17,035)
Unrealized gains (losses) on investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	[1]	730,429	803,094
OCI before reclassifications	[1]	149,959	575,022
Amounts reclassified from AOCI	[1]	(52,554)	(117,114)
Tax benefit (expense)	[1]	(10,952)	(34,707)
Comprehensive income (loss)	[1]	86,453	423,201
Ending balance, net of tax	[1]	816,882	1,226,295
Cumulative impact of net unrealized gains losses on future policy benefit reserve		207,000		$ 212,100
Change in adjustments related to future policy benefit reserves, net of tax		(5,100)
OTTI losses recognized in AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax		(50,952)	(57,502)
OCI before reclassifications		0	0
Amounts reclassified from AOCI		1,455	2,311
Tax benefit (expense)		(13)	(44)
Comprehensive income (loss)		1,442	2,267
Ending balance, net of tax		(49,510)	(55,235)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax		58,970	(36,503)
OCI before reclassifications		39,204	(15,416)
Amounts reclassified from AOCI		0	0
Tax benefit (expense)		2,734	(1,023)
Comprehensive income (loss)		41,938	(16,439)
Ending balance, net of tax		100,908	(52,942)
Underfunded pension liability
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax		(24,887)	(24,641)
OCI before reclassifications		(341)	(1,049)
Amounts reclassified from AOCI		0	0
Tax benefit (expense)		(16)	0
Comprehensive income (loss)		(357)	(1,049)
Ending balance, net of tax		(25,244)	(25,690)
Cash flow hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax		1,986	2,168
OCI before reclassifications		0	0
Amounts reclassified from AOCI		(48)	(39)
Tax benefit (expense)		0	0
Comprehensive income (loss)		(48)	(39)
Ending balance, net of tax		$ 1,938	$ 2,129

[1] For certain annuity contracts that are subject to the GreyCastle Life Retro Arrangements, policy benefit reserves were historically increased for the impact of changes in unrealized gains on investments supporting such contracts as if the gains had been realized, with a corresponding entry to other comprehensive income ("Shadow Adjustments"). Upon completion of the GreyCastle Life Retro Arrangements, no further Shadow Adjustments were recorded. At December 31, 2016, the cumulative impact of the Shadow Adjustments was $212.1 million. During the three months ended March 31, 2017, net movements of $(5.1) million were recorded, resulting in a total cumulative net impact of Shadow Adjustments on future policy benefit reserves of $207.0 million at March 31, 2017.