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Common Stock Dividends (Narrative) (Details) - $ / shares
3 Months Ended 6 Months Ended
Sep. 08, 2015
Jun. 01, 2015
Apr. 06, 2015
Feb. 19, 2015
Jul. 31, 2015
Jul. 31, 2014
Jul. 31, 2015
Jul. 31, 2014
Dividends Payable [Line Items]                
Common stock, quarterly dividends, per share, declared       $ 0.49        
Annual dividend approved by Board of Directors       $ 1.96 $ 0.00 $ 0.00 $ 1.96 $ 1.92
Dividend Paid [Member]                
Dividends Payable [Line Items]                
Dividends   Jun. 01, 2015 Apr. 06, 2015          
Subsequent event | Dividend Paid [Member]                
Dividends Payable [Line Items]                
Dividends Sep. 08, 2015