Income Taxes (Reconciliation To Effective Rate) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Expected federal income tax expense				$ 112,472	$ 174,077	$ 320,866
Non-taxable investment income				(146,324)	(161,407)	(152,844)
Tax credits				(30,916)	(24,232)	(32,881)
Domestic production activities deduction, net				(9,488)	0	0
Other				387	921	1,928
Total income tax expense (benefit)	$ 5,055	$ (44,108)	$ (39,053)	$ (73,869)	$ (10,641)	$ 137,069