Recent Accounting Pronouncements (Details) $ in Millions	Dec. 31, 2017 USD ($)
Accounting Standards Update 2018-02 | New Accounting Pronouncement, Early Adoption, Effect | Accumulated Other Comprehensive Loss
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment of ASU adoption	$ (3)
Accounting Standards Update 2018-02 | New Accounting Pronouncement, Early Adoption, Effect | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment of ASU adoption	3
Accounting Standards Update 2017-12 | New Accounting Pronouncement, Early Adoption, Effect | Accumulated Other Comprehensive Loss
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment of ASU adoption	3
Accounting Standards Update 2017-12 | New Accounting Pronouncement, Early Adoption, Effect | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment of ASU adoption	(3)
Accounting Standards Update 2014-09 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment of ASU adoption	$ 208