Long-Term Debt (Debt Issues) (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Jul. 30, 2016
Jan. 28, 2017
Apr. 30, 2016
Jan. 30, 2016
Debt Instrument [Line Items]        
Total debt, excluding unamortized debt issuance costs, capital leases and note payable   $ 4,665   $ 4,830
Total debt, excluding unamortized debt issuance costs, capital leases, financing obligation and note payable   4,602   4,769
Unamortized Debt Issuance Expense   (63)   (61)
Less: current maturities   263   101
Total long-term debt, excluding capital leases, financing obligation and note payable   $ 4,339   $ 4,668
Weighted-average interest rate at year end   6.30%   6.50%
Weighted-average maturity (in years)   15 years    
Debt Instrument, Repurchased Face Amount     $ 60  
5.65% Senior Notes Due 2020 (1)        
Debt Instrument [Line Items]        
Debt instrument, stated interest rate (percent)   5.65%   5.65%
Unsecured Long-term Debt, Noncurrent [1]   $ 400   $ 400
5.75% Senior Notes Due 2018 (1)        
Debt Instrument [Line Items]        
Debt instrument, stated interest rate (percent)   5.75%   5.75%
Unsecured Long-term Debt, Noncurrent [1]   $ 265   $ 300
Senior Secured Notes Five Point Eight Seven Five Percent Due2023 [Member]        
Debt Instrument [Line Items]        
Debt instrument, stated interest rate (percent)   5.875%    
Secured Debt [1]   $ 500    
6.375% Senior Notes Due 2036 (1)        
Debt Instrument [Line Items]        
Debt instrument, stated interest rate (percent)   6.375%   6.375%
Unsecured Long-term Debt, Noncurrent [1]   $ 388   $ 400
6.9% Notes Due 2026        
Debt Instrument [Line Items]        
Debt instrument, stated interest rate (percent)   6.90%   6.90%
Unsecured Long-term Debt, Noncurrent   $ 2   $ 2
7.125% Debentures Due 2023        
Debt Instrument [Line Items]        
Debt instrument, stated interest rate (percent)   7.125%   7.125%
Unsecured Long-term Debt, Noncurrent   $ 10   $ 10
7.4% Debentures Due 2037        
Debt Instrument [Line Items]        
Debt instrument, stated interest rate (percent)   7.40%   7.40%
Unsecured Long-term Debt, Noncurrent   $ 313   $ 326
7.625% Notes Due 2097        
Debt Instrument [Line Items]        
Debt instrument, stated interest rate (percent)   7.625%   7.625%
Unsecured Long-term Debt, Noncurrent   $ 500   $ 500
7.65% Debentures Due 2016        
Debt Instrument [Line Items]        
Debt instrument, stated interest rate (percent)   7.65%   7.65%
Unsecured Long-term Debt, Noncurrent   $ 0   $ 78
7.95% Debentures Due 2017        
Debt Instrument [Line Items]        
Debt instrument, stated interest rate (percent)   7.95%   7.95%
Unsecured Long-term Debt, Noncurrent   $ 220   $ 220
2013 Term Loan Facility        
Debt Instrument [Line Items]        
Secured Debt       2,194
Debt Instrument, Repurchased Face Amount $ 2,250      
Total debt, excluding unamortized debt issuance costs, capital leases, financing obligation and note payable        
Debt Instrument [Line Items]        
Total debt, excluding unamortized debt issuance costs, capital leases and note payable   $ 4,665   $ 4,830
Senior notes        
Debt Instrument [Line Items]        
Debt repurchase provision, percentage of outstanding principal   101.00%    
Debt repurchase provision, required beneficial ownership change   50.00%    
8.125% Senior Notes Due 2019        
Debt Instrument [Line Items]        
Debt instrument, stated interest rate (percent)   8.125%   8.125%
Unsecured Long-term Debt, Noncurrent   $ 400   $ 400
2016 Term Loan Facility [Member]        
Debt Instrument [Line Items]        
Secured Debt   $ 1,667    
2016 Term Loan Facility [Member]        
Debt Instrument [Line Items]        
2013 Term Loan Facility, term 7 years      
[1] These debt issuances contain a change of control provision that would obligate us, at the holders’ option, to repurchase the debt at a price of 101%. These provisions trigger if there were a beneficial ownership change of 50% or more of our common stock.