Description of Business and Significant Accounting Policies - Adoption of ASU 2016-02 (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
New Accounting Pronouncement, Early Adoption [Line Items]
Operating lease right-of-use assets	$ 55
Operating lease liabilities	17
Operating lease liabilities, noncurrent	48
Accumulated deficit	(219)	$ (266)
Calculated Under Guidance In Effect Before Topic 842
New Accounting Pronouncement, Early Adoption [Line Items]
Operating lease liabilities, noncurrent	10
Accumulated deficit	(219)
Accounting Standards Update 2016-02 | Difference Between Guidance In Effect Before And After Topic 842
New Accounting Pronouncement, Early Adoption [Line Items]
Operating lease right-of-use assets	55
Operating lease liabilities	17
Operating lease liabilities, noncurrent	38
Accumulated deficit	$ 0