Consolidated Statements of Comprehensive Income (Unaudited) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]        
Net income attributable to common stockholders $ 148 $ 174 $ 367 $ 377
Pension amortized to periodic benefit cost:        
Actuarial loss, net of tax of $1 for the three months and $3 for the nine months 1 1 4 4
Foreign currency translation adjustment       (1)
Unrealized loss on cash flow hedges, net of tax of $(3) and $0 for the three months and $(10) and $0 for the nine months (4)   (15)  
Net other comprehensive income (loss) (3) 1 (11) 3
Comprehensive income attributable to common stockholders $ 145 $ 175 $ 356 $ 380