Supplemental Equity and Comprehensive Income Information (Details 7) - USD ($) $ / shares in Units, $ in Billions	1 Months Ended		3 Months Ended				6 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2015	Jun. 30, 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	$ 1.025	$ 0.855	$ 0.855	$ 2.05	$ 1.71
Increase of Current Liabilities due to dividend declared but not paid	$ 0.6	$ 0.6