Income Taxes (Components of Income Tax Expense (Benefit)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current tax expense (benefit):
U.S. Federal	$ 56,371	$ 36,739	$ (52,502)
Total	56,371	36,739	(52,502)
Deferred tax expense (benefit):
U.S. Federal	(115,503)	(89,380)	(104,326)
Total	(115,503)	(89,380)	(104,326)
Total income tax expense (benefit) on income (loss) before equity in earnings of operating joint ventures	(59,132)	(52,641)	(156,828)
Income tax expense (benefit) on equity in earnings of operating joint ventures	(1,773)	648	0
Income tax expense (benefit) reported in equity related to:
Other comprehensive income (loss)	81,281	(55,174)	43,372
Additional paid-in capital	0	0	824
Total income tax expense (benefit)	$ 20,376	$ (107,167)	$ (112,632)