Accumulated Other Comprehensive Income (Loss) - Changes in AOCI, net of tax (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2015		Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	$ 1,705,170		$ 946,661	$ 1,484,458		$ 736,657
OCI before Reclassifications	(581,964)		359,719	(294,319)		619,039
Amounts reclassified from AOCI	(85,884)		(72,587)	(150,633)		(91,706)
Tax benefit (expense)	38,852		(26,759)	36,668		(56,956)
Comprehensive income (loss)	(628,996)		260,373	(408,284)		470,377
Ending balance, net of tax	1,076,174		1,207,034	1,076,174		1,207,034
AOCI Other Details [Abstract]
Change in adjustments related to future policy benefit reserves, net of tax	(26,328)		440,461	(86,684)		474,465
Unrealized gains (losses) on investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	1,763,795	[1]	1,032,941	1,590,114	[1]	822,432
OCI before Reclassifications	(544,273)	[1]	363,348	(290,007)	[1]	628,599
Amounts reclassified from AOCI	(87,558)	[1]	(74,337)	(162,338)	[1]	(96,975)
Tax benefit (expense)	37,000	[1]	(20,774)	31,195	[1]	(52,878)
Comprehensive income (loss)	(594,831)	[1]	268,237	(421,150)	[1]	478,746
Ending balance, net of tax	1,168,964	[1]	1,301,178	1,168,964	[1]	1,301,178
AOCI Other Details [Abstract]
Change in adjustments related to future policy benefit reserves, net of tax				(86,700)
Cumulative impact on value of future policy benefit reserve, end of period	358,400			358,400			$ 445,100
OTTI losses recognized in AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	(66,189)		(85,894)	(76,047)		(89,190)
OCI before Reclassifications	0		0	0		0
Amounts reclassified from AOCI	1,662		1,640	11,598		5,049
Tax benefit (expense)	(87)		(4)	(165)		(117)
Comprehensive income (loss)	1,575		1,636	11,433		4,932
Ending balance, net of tax	(64,614)		(84,258)	(64,614)		(84,258)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	24,915		10,661	(11,188)		14,541
OCI before Reclassifications	(36,362)		(3,621)	(3,958)		(9,521)
Amounts reclassified from AOCI	0		0	0		0
Tax benefit (expense)	1,939		(5,981)	5,638		(3,961)
Comprehensive income (loss)	(34,423)		(9,602)	1,680		(13,482)
Ending balance, net of tax	(9,508)		1,059	(9,508)		1,059
Underfunded pension liability
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	(19,814)		(13,270)	(20,789)		(13,239)
OCI before Reclassifications	(1,329)		(8)	(354)		(39)
Amounts reclassified from AOCI	0		0	0		0
Tax benefit (expense)	0		0	0		0
Comprehensive income (loss)	(1,329)		(8)	(354)		(39)
Ending balance, net of tax	(21,143)		(13,278)	(21,143)		(13,278)
Cash flow hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	2,463		2,223	2,368		2,113
OCI before Reclassifications	0		0	0		0
Amounts reclassified from AOCI	12		110	107		220
Tax benefit (expense)	0		0	0		0
Comprehensive income (loss)	12		110	107		220
Ending balance, net of tax	$ 2,475		$ 2,333	$ 2,475		$ 2,333

[1] Included in these amounts is the impact of Shadow Adjustments. As of December 31, 2014 the cumulative impact of the Shadow Adjustments was $445.1 million. During the six months ended June 30, 2015, net movements of $(86.7) million were recorded, resulting in a total cumulative net impact of Shadow Adjustments on future policy benefit reserves of $358.4 million as of June 30, 2015.