Investments (Balance of and Changes in AOCI Components) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance			$ 64,805
Income tax benefit (expense)	$ 5,499	$ (21,706)	49,594	$ (35,052)
Balance	241,016		241,016		$ 64,805
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance			(397)	(67)	(67)
Change in OCI before reclassifications			121	(338)
Amounts reclassified from AOCI			0	0
Income tax benefit (expense)			(42)	118
Balance	(318)	(287)	(318)	(287)	(397)	$ (67)
Total net unrealized investment gains (losses)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance			65,202	178,758	178,758
Change in OCI before reclassifications			344,649	(123,909)
Amounts reclassified from AOCI	(88,601)	(1,930)	(73,677)	(4,044)
Income tax benefit (expense)			(94,840)	44,582
Balance	241,334	95,387	241,334	95,387	65,202	178,758
Cash Flow Hedge Gain (Loss) To AOCI			38,000	24,000	48,000	12,000
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance			64,805	178,691	178,691
Change in OCI before reclassifications			344,770	(124,247)
Amounts reclassified from AOCI	(88,601)	(1,930)	(73,677)	(4,044)
Income tax benefit (expense)			(94,882)	44,700
Balance	$ 241,016	$ 95,100	$ 241,016	$ 95,100	$ 64,805	$ 178,691