Investments - Schedule of Changes in Assets Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 601,188	$ 575,946
Total gains or losses:
Included in realized gains/losses	0	0
Included in other comprehensive income	19,460	5,105
Acquisitions	15,800	19,400
Sales	0	0
Amortization	2,647	2,817
Other	(5,867)	(7,571)
Transfers in and/or out of Level 3	0	0
Ending balance	$ 633,228	$ 595,697
Percent of total fixed maturities	4.10%	4.20%
Collateralized debt obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 70,382	$ 63,232
Total gains or losses:
Included in realized gains/losses	0	0
Included in other comprehensive income	(4,831)	13,531
Acquisitions	0	0
Sales	0	0
Amortization	2,639	2,810
Other	(4,127)	(5,905)
Transfers in and/or out of Level 3	0	0
Ending balance	$ 64,063	$ 73,668
Percent of total fixed maturities	0.40%	0.50%
Corporates [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 530,806	$ 512,714
Total gains or losses:
Included in realized gains/losses	0	0
Included in other comprehensive income	24,291	(8,426)
Acquisitions	15,800	19,400
Sales	0	0
Amortization	8	7
Other	(1,740)	(1,666)
Transfers in and/or out of Level 3	0	0
Ending balance	$ 569,165	$ 522,029
Percent of total fixed maturities	3.70%	3.70%