New Accounting Guidance - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability	$ 2,232
Operating lease, right-of-use asset	$ 1,885	$ 1,921
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability			$ 1,900
Operating lease, right-of-use asset			1,700
Accounting Standards Update 2016-02 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other liabilities			$ 200