Summary of Significant Accounting Policies Textuals (Details) $ in Millions	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Accounting Policies [Abstract]
Minimum fixed charge coverage ratio		1.25
Summary Of Significant Accounting Policies [Line Items]
Decrease in receivable reserves		$ (162)	$ (167)	$ (145)	$ (110)
Current and deferred tax impact		(21)	(37)
Retained earnings, net of tax		$ 3,513	$ 3,095
ASU 2016-13 | Forecast [Member] | Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Decrease in receivable reserves	$ 147
Increase in loan reserves	7
Current and deferred tax impact	24
Retained earnings, net of tax	$ 116