Equity (Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 64,805
Income tax benefit (expense)	(3,322)	$ 61,322	$ (65,717)
Ending balance	70,975	64,805
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(397)	(67)	403
Change in other comprehensive income before reclassifications	(8)	(507)	(723)
Amounts reclassified from AOCI	0	0	0
Income tax benefit (expense)	3	177	253
Ending balance	(402)	(397)	(67)
Net Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	65,202	178,758	56,243
Change in other comprehensive income before reclassifications	74,040	(164,799)	207,134
Amounts reclassified from AOCI	(64,540)	(9,902)	(18,649)
Income tax benefit (expense)	(3,325)	61,145	(65,970)
Ending balance	71,377	65,202	178,758
Total Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	64,805	178,691	56,646
Change in other comprehensive income before reclassifications	74,032	(165,306)	206,411
Amounts reclassified from AOCI	(64,540)	(9,902)	(18,649)
Income tax benefit (expense)	(3,322)	61,322	(65,717)
Ending balance	70,975	64,805	178,691
Cash flow hedges | Net Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	48,000	12,000
Ending balance	$ 41,000	$ 48,000	$ 12,000