New Accounting Guidance - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2020	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Operating lease, liability		$ 2,237
Operating lease, right-of-use asset	$ 1,921	$ 1,884
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability			$ 1,900
Operating lease, right-of-use asset			1,700
Other liabilities			$ 200