Summary of Significant Accounting Policies - Narrative (Details) $ in Millions			3 Months Ended	9 Months Ended
	Jan. 01, 2020 USD ($)	Jan. 01, 2019 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2019 segment
Accounting Policies [Abstract]
Number of operating segments | segment				2
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards			$ 40
Right-of-Use Assets [Member] | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards		$ 129
Lease Obligations [Member] | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards		$ 144
Forecast [Member] | Minimum [Member] | Allowance For Credit Losses [Member] | Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards	$ 700
Forecast [Member] | Minimum [Member] | Retained Earnings [Member] | Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards	500
Forecast [Member] | Maximum [Member] | Allowance For Credit Losses [Member] | Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards	900
Forecast [Member] | Maximum [Member] | Retained Earnings [Member] | Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards	$ 700