Income Taxes (Reconciliation To Effective Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%
Expected federal income tax expense (benefit)	$ 387,286	$ 391,158	$ (619,704)
Non-taxable investment income	(18,954)	(46,625)	(49,630)
Tax credits	(13,694)	(10,358)	(10,507)
Changes in tax law	(193,306)	882,175	0
Other	172	(15,251)	(652)
Total income tax expense (benefit)	$ 161,504	$ 1,201,099	$ (680,493)
Effective tax rate	8.80%	107.50%	38.40%