Changes in Accounting Principles (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Aggregate operating lease ROU asset	$ 44	$ 45
Cumulative effective of accounting principle		1	$ (30)
Operating lease, liability	$ 44	45
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effective of accounting principle		$ 1