Accumulated Other Comprehensive Income (Loss) - Changes in AOCI, net of tax (Details) (USD $)	3 Months Ended			12 Months Ended
	Mar. 31, 2014		Mar. 31, 2013	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	$ 736,657,000		$ 1,520,020,000	$ 1,520,020,000
OCI before Reclassifications	259,319,000		(92,355,000)
Amounts reclassified from AOCI	(19,119,000)		(36,400,000)
Tax (benefit) expense	(30,196,000)		13,857,000
Net current period OCI - net of tax	210,004,000		(114,898,000)
Ending balance, net of tax	946,661,000		1,405,122,000
Unrealized gains (losses) on investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	822,439,000	[1]	1,591,218,000	1,591,218,000
OCI before Reclassifications	265,251,000	[1]	(87,687,000)
Amounts reclassified from AOCI	(22,638,000)	[1]	(41,695,000)
Tax (benefit) expense	(32,103,000)	[1]	12,726,000
Net current period OCI - net of tax	210,510,000	[1]	(116,656,000)
Ending balance, net of tax	1,032,949,000	[1]	1,474,562,000	822,439,000	[1]
AOCI Other Details [Abstract]
Adjustments recorded to the value of future policy benefit reserves	34,000,000			44,700,000
Cumulative impact on value of future policy benefit reserve, end of period	78,700,000
OTTI losses recognized in AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	(89,190,000)		(121,371,000)	(121,371,000)
OCI before Reclassifications	0		0
Amounts reclassified from AOCI	3,409,000		5,185,000
Tax (benefit) expense	(113,000)		(3,000)
Net current period OCI - net of tax	3,296,000		5,182,000
Ending balance, net of tax	(85,894,000)		(116,189,000)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	14,533,000		69,391,000	69,391,000
OCI before Reclassifications	(5,900,000)		(5,053,000)
Amounts reclassified from AOCI	0		0
Tax (benefit) expense	2,020,000		1,134,000
Net current period OCI - net of tax	(3,880,000)		(3,919,000)
Ending balance, net of tax	10,653,000		65,472,000
Underfunded pension liability
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	(13,238,000)		(20,892,000)	(20,892,000)
OCI before Reclassifications	(32,000)		385,000
Amounts reclassified from AOCI	0		0
Tax (benefit) expense	0		0
Net current period OCI - net of tax	(32,000)		385,000
Ending balance, net of tax	(13,270,000)		(20,507,000)
Cash flow hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	2,113,000		1,674,000	1,674,000
OCI before Reclassifications	0		0
Amounts reclassified from AOCI	110,000		110,000
Tax (benefit) expense	0		0
Net current period OCI - net of tax	110,000		110,000
Ending balance, net of tax	$ 2,223,000		$ 1,784,000

[1] Included in these amounts are the impact of net unrealized gains (losses) on investments to the value of future policy benefit reserves. During the year ended December 31, 2013, the initial impact of $44.7 million was recorded. During the three months ended March 31, 2014, additional impacts of $34.0 million were recorded, resulting in a total cumulative impact of net unrealized gains (losses) on investments to the value of future policy benefit reserves of $78.7 million at March 31, 2014.