Supplemental Equity and Comprehensive Income Information (Details 7) (USD $)
In Billions, except Per Share data, unless otherwise specified
1 Months Ended 3 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Mar. 31, 2015
Mar. 31, 2014
Supplemental Equity and Comprehensive Income Information        
Dividends that have been declared but not yet paid (in dollars per share) $ 1.025 $ 0.855    
Dividends paid in current period (in dollars per share)     $ 1.025 $ 0.855
Increase of Current Liabilities due to dividend declared but not paid $ 0.6 $ 0.6