Pensions and Other Postretirement Benefits (Tables)
 9 Months Ended
Sep. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]  
Defined Contribution Plan Disclosures
 
Three Months Ended
September 30
 
Nine Months Ended
September 30
($ in millions)
2016
 
2015
 
2016
 
2015
U.S. defined benefit pension contributions
$
50

 
$
—

 
$
50

 
$
250

Non-U.S. defined benefit pension voluntary contributions
$
—

 
$
—

 
$
—

 
$
21

Non-U.S. defined benefit pension mandatory contributions
$
15

 
$
—

 
$
28

 
$
15
Pension Plan [Member]  
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]  
Net Periodic Benefit Cost
The net periodic pension and other post-retirement benefit costs for the three and nine months ended September 30, 2016 and 2015 were as follows:
 
Pensions
 
Three Months Ended
September 30
 
Nine Months Ended
September 30
($ in millions)
2016
 
2015
 
2016
 
2015
Service cost
$
11

 
$
14

 
$
38

 
$
42

Interest cost
21

 
48

 
108

 
150

Expected return on plan assets
(31
)
 
(76
)
 
(169
)
 
(209
)
Amortization of actuarial losses
24

 
34

 
85

 
84

Amortization of prior service credit
(1
)
 
(1
)
 
(2
)
 
(2
)
Pension settlement charges
968

 
7

 
968

 
7

Curtailments and special termination benefits
—

 
1

 
—

 
2

Net periodic benefit cost
$
992

 
$
27

 
$
1,028

 
$
74
Other Postretirement Benefit Plan [Member]  
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]  
Net Periodic Benefit Cost
 
Other Postretirement Benefits
 
Three Months Ended
September 30
 
Nine Months Ended
September 30
($ in millions)
2016
 
2015
 
2016
 
2015
Service cost
$
8

 
$
4

 
$
14

 
$
13

Interest cost
12

 
11

 
30

 
35

Amortization of actuarial losses
10

 
7

 
20

 
23

Amortization of prior service credit
(28
)
 
(2
)
 
(32
)
 
(7
)
Net periodic benefit cost
$
2

 
$
20

 
$
32

 
$
64