Background (Details) $ in Millions	1 Months Ended	3 Months Ended
	May 10, 2019 USD ($)	Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)	Jan. 01, 2019 USD ($)
New Accounting Pronouncement, Early Adoption [Line Items]
Number of reportable segments | segment		1
Operating lease assets		$ 1,246
Operating lease liability		1,293
Payments of dividends		$ 225	$ 390
Subsequent Event
New Accounting Pronouncement, Early Adoption [Line Items]
Payments of dividends	$ 90
Accounting Standards Update 2016-02
New Accounting Pronouncement, Early Adoption [Line Items]
Operating lease assets				$ 1,300
Operating lease liability				$ 1,400