Description of Business and Significant Accounting Policies - Effect of Adoption of ASU 2016-02 As Reported (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncement, Early Adoption [Line Items]
Operating lease right-of-use asset	$ 59,000,000	$ 0
Operating lease liabilities	16,000,000	0
Operating lease liabilities, noncurrent	54,000,000	0
Accumulated deficit	(245,000,000)	$ (266,000,000)
Balance Using Previous Standard
New Accounting Pronouncement, Early Adoption [Line Items]
Operating lease right-of-use asset	0
Operating lease liabilities	0
Operating lease liabilities, noncurrent	11,000,000
Accumulated deficit	(245,000,000)
Accounting Standards Update 2016-02 | Increase (Decrease)
New Accounting Pronouncement, Early Adoption [Line Items]
Operating lease right-of-use asset	59,000,000
Operating lease liabilities	16,000,000
Operating lease liabilities, noncurrent	43,000,000
Accumulated deficit	$ 0