Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2017	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%
Deferred Tax Assets, Valuation Allowance	$ (3,192)		$ (3,094)
Effective income tax rate	1.90%