Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions		Mar. 31, 2019	Jan. 01, 2019
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Operating lease right of use assets		$ 66
Operating lease liabilities	[1]	$ 78
ASU 2016-02
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Operating lease right of use assets			$ 68
Operating lease liabilities			$ 80

[1] Operating lease payments exclude $2 million of legally binding minimum lease payments for leases signed but not yet commenced.