XML 59 R49.htm IDEA: XBRL DOCUMENT v3.8.0.1
Fair Value Measurements Changes in Fair Value Level 3 (Details) - Recurring measurement - Level 3 - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, [Roll Forward]        
Fair value of assets measured at fair value on a recurring basis $ 302 $ 214 $ 279 $ 212
Fair value, measurement with unobservable inputs reconciliation, recurring basis, assets, unrealized gain (loss) 23 1    
Transfers in $ 0 $ 1