Retirement Benefit Plans (Net Periodic Expense) (Details)
$ in Millions
 1 Months Ended 3 Months Ended 9 Months Ended
Nov. 16, 2015
Nov. 05, 2015
Aug. 03, 2015
employee
Dec. 07, 2015
Oct. 31, 2015
USD ($)
employee
Nov. 01, 2014
USD ($)
Oct. 31, 2015
USD ($)
Nov. 01, 2014
USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]                
Net periodic benefit expense/(income)         $ 12 $ 1 $ 35 $ 4
Transfer of benefits           25    
Number of participants in the Primary Pension Plan who separated from service and had a deferred vested benefit as of August 31, 2012 who were offered the option to receive a lump-sum settlement payment | employee     8,000   1,900      
Number of retirees and beneficiaries in the Primary Pension Plan who commenced their benefit between January 1, 2000 and August 31, 2012 who were offered the option to receive a lump-sum settlement payment | employee     31,000   12,000      
Primary Pension Plan                
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]                
Service cost         $ 17 15 52 46
Interest cost         49 53 147 158
Other cost         2 0 5 0
Expected return on plan assets         (89) (87) (267) (261)
Amortization of actuarial loss/(gain)         26 13 77 38
Amortization of prior service cost/(credit)         2 1 6 5
Loss/(gain) on transfer of benefits         0 6 0 6
Net periodic benefit expense/(income)         7 1 20 (8)
Supplemental Pension Plans                
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]                
Service cost         0 0 0 0
Interest cost         2 3 5 7
Amortization of actuarial loss/(gain)         3 3 10 11
Amortization of prior service cost/(credit)         0 0 0 0
Loss/(gain) on transfer of benefits         0 (6) 0 (6)
Net periodic benefit expense/(income)         5 0 15 12
Primary and Supplemental Pension Plans Total                
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]                
Service cost         17 15 52 46
Interest cost         51 56 152 165
Other cost         2 0 5 0
Expected return on plan assets         (89) (87) (267) (261)
Amortization of actuarial loss/(gain)         29 16 87 49
Amortization of prior service cost/(credit)         2 1 6 5
Loss/(gain) on transfer of benefits         0 0 0 0
Net periodic benefit expense/(income)         12 1 35 4
Postretirement Health and Welfare Plan                
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]                
Service cost         0 0 0 0
Interest cost         0 0 0 0
Amortization of actuarial loss/(gain)         0 0 0 0
Amortization of prior service cost/(credit)         (2) (2) (6) (6)
Net periodic benefit expense/(income)         (2) (2) (6) (6)
Retirement Benefit Plans Total [Member]                
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]                
Service cost         17 15 52 46
Interest cost         51 56 152 165
Other cost         2 0 5 0
Expected return on plan assets         (89) (87) (267) (261)
Amortization of actuarial loss/(gain)         29 16 87 49
Amortization of prior service cost/(credit)         0 (1) 0 (1)
Loss/(gain) on transfer of benefits         0 0 0 0
Net periodic benefit expense/(income)         $ 10 $ (1) $ 29 $ (2)
Subsequent Event [Member]                
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]                
Subsequent Event, Description On November 16, 2015, the Company announced that it has received $500 million of incremental bank commitments to increase the size of the Revolving Facility under the 2014 Credit Facility to $2,350 million. In connection with upsizing the Revolving Facility, the Company also intends to prepay and retire the outstanding principal amount of the 2014 Term Loan. The lump-sum settlement payments were made by the Company on November 5, 2015 using assets from the Primary Pension Plan.  Accordingly, the settlement expense related to the lump sum payments will be recognized in the fourth quarter of 2015.   The Company has also entered into a definitive agreement to purchase a group annuity contract from The Prudential Insurance Company of America (Prudential), under which Prudential will pay and administer future benefit payments to select retirees. The agreement provides for the Primary Pension Plan to transfer a portion of its obligations and assets to Prudential. The annuity transaction closed on December 7, 2015, and the Company has an option to transfer additional portions in 2016 if market conditions warrant.        
Subsequent Event, Date Nov. 16, 2015 Nov. 05, 2015   Dec. 07, 2015