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)
Beginning Balance	$ 46,166
Income tax benefit (expense)	680,493	$ 8,285	$ (8,604)
Ending Balance	(314,948)	46,166
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	(65)	(30)	10
Change in other comprehensive income before reclassifications	(20)	(54)	(63)
Amounts reclassified from AOCI	0	0	0
Income tax benefit (expense)	7	19	23
Ending Balance	(78)	(65)	(30)
Net Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	46,231	84,652	70,857
Change in other comprehensive income before reclassifications	(469,356)	(54,279)	35,931
Amounts reclassified from AOCI	(86,184)	(4,831)	(14,706)
Income tax benefit (expense)	194,439	20,689	(7,430)
Ending Balance	(314,870)	46,231	84,652
Total Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	46,166	84,622	70,867
Change in other comprehensive income before reclassifications	(469,376)	(54,333)	35,868
Amounts reclassified from AOCI	(86,184)	(4,831)	(14,706)
Income tax benefit (expense)	194,446	20,708	(7,407)
Ending Balance	(314,948)	46,166	84,622
Cash flow hedges | Net Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	15,000	5,000
Ending Balance	$ 12,000	$ 15,000	$ 5,000