Retirement Benefit Plans (Tables)
 3 Months Ended
Apr. 30, 2016
Retirement Benefit Plans [Abstract]  
Schedule of Pension Plan Expense/(Income)
he components of net periodic benefit expense/(income) for our non-contributory qualified defined benefit pension plan (Primary Pension Plan) and non-contributory supplemental pension plans were as follows:
 
Three Months Ended
($ in millions)
April 30,
2016
 
May 2,
2015
Primary Pension Plan
 
 
 
Service cost
$
14

 
$
17

Interest cost
38

 
49

Expected return on plan assets
(54
)
 
(89
)
Amortization of prior service cost/(credit)
2

 
2

Net periodic benefit expense/(income)
$
—

 
$
(21
)
 
 
 
 
Supplemental Pension Plans
 
 
 
Interest cost
2

 
2

Net periodic benefit expense/(income)
$
2

 
$
2

 
 
 
 
Primary and Supplemental Pension Plans Total
 
 
 
Service cost
$
14

 
$
17

Interest cost
40

 
51

Expected return on plan assets
(54
)
 
(89
)
Amortization of prior service cost/(credit)
2

 
2

Net periodic benefit expense/(income)
$
2

 
$
(19
)