XML 50 R36.htm IDEA: XBRL DOCUMENT v3.10.0.1
Significant Accounting Policies - Cash and Cash Equivalents (Details) - USD ($)
$ in Millions
Jun. 30, 2018
Dec. 31, 2017
Jun. 30, 2017
Dec. 31, 2016
Accounting Policies [Abstract]        
Cash and cash equivalents $ 3,392 $ 3,186 $ 2,979  
Restricted cash and cash equivalents 98   92  
Cash and cash equivalents reported in assets held for sale 9   0  
Total cash, cash equivalents, and restricted cash and cash equivalents presented in the statements of cash flows $ 3,499 $ 3,290 $ 3,071 $ 2,912