Stockholders' Equity - New Accounting Pronouncements (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of ASU	$ (4)	$ 66
Accumulated deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of ASU	$ (4)	175
Accumulated other comprehensive loss
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of ASU		(109)
Accounting Standards Update 2017-05 | Accumulated deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of ASU		66
Accounting Standards Update 2018-02 | Accumulated deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of ASU		109
Accounting Standards Update 2018-02 | Accumulated other comprehensive loss
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of ASU		$ (109)