Income Taxes - Breakdown of Income Tax Expense Between Current and Deferred (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018
Current:
Federal	$ 559	$ 608		$ 572
State	123	104		144
Subtotal Current	682	712		716
Deferred:
Federal	149	235		275
State	31	38		4
Subtotal Deferred	180	273		279
Total Income Tax Expense	$ 862	$ 985	[1]	$ 995	[1]

[1] Certain prior year data has been reclassified to conform to the current presentation.