Description of Business, Basis of Presentation, and Changes in Significant Accounting Policies Description of Business, Basis of Presentation, and Changes in Significant Accounting Policies (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Accounting Standards Adopted or Issued [Abstract]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 14	$ 16