Accounting Policies (Details) - USD ($) $ in Millions	Jan. 01, 2019	Sep. 30, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liability		$ 2,164
Operating lease asset		$ 2,000
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liability	$ 2,100
Operating lease asset	2,000
Accounting Standards Update 2016-02 [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of ASU adoptions, pretax	$ 83