Income Taxes (Tables)
 9 Months Ended
Sep. 30, 2016
Income Tax Disclosure [Abstract]  
Schedule of Components of Income Tax Provision (Benefit)
 
Three Months Ended September 30,
 
Nine Months Ended September 30,
 
2016
2015
 
2016
2015
 
(Dollars in millions)
Provision for income taxes
$
30

$
24

 
$
73

$
70

Effective tax provision rate
34.3
%
34.4
%
 
33.8
%
36.0
%