Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ (24,651)	$ (862,080)	$ 469,300	$ (1,099,568)
Effective income tax rate, percent			20.54%	29.91%
Federal Statutory income tax rate, percent			21.00%		35.00%
CARES Act NOL Carryback				$ 305,000