Quarterly report pursuant to Section 13 or 15(d)

Organization and Operations (Details)

v3.8.0.1
Organization and Operations (Details) - USD ($)
$ in Millions
Mar. 31, 2018
Dec. 31, 2017
Mar. 31, 2017
Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]        
Restricted cash and cash equivalents $ 16 $ 17 $ 12 $ 6
Accounting Standards Codification Topic 606        
New Accounting Pronouncements or Change in Accounting Principle [Line Items]        
Cumulative effect adjustment to retained earnings 16      
Retained Earnings | Accounting Standards Codification Topic 606        
New Accounting Pronouncements or Change in Accounting Principle [Line Items]        
Cumulative effect adjustment to retained earnings $ 16