Significant Accounting Policies (Details) $ in Millions	Jan. 01, 2018 USD ($)
Revenue from Contracts with Customers
Accounting Standards Adopted
Cumulative catch-up adjustment to Retained Earnings	$ (32)
Derivatives and Hedging-Targeted Improvements to Accounting for Hedging Activities
Accounting Standards Adopted
Cumulative catch-up adjustment to Retained Earnings	(99)
Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income
Accounting Standards Adopted
Cumulative catch-up adjustment to Retained Earnings	$ 443