Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended		3 Months Ended
	Feb. 29, 2016	Jan. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Stockholders Equity [Line Items]
Common stock, shares issued				524.0		418.0
Net proceeds from offering				$ 1,469
Payments of ordinary dividends				$ 125	$ 99
Dividends paid per share				$ 0.24
Forecast [Member]
Stockholders Equity [Line Items]
Dividends paid per share			$ 0.06
Common Stock Offering [Member]
Stockholders Equity [Line Items]
Common stock, shares issued	79.0
Net proceeds from offering	$ 1,500
Common Stock Offering [Member] | Underwriters [Member]
Stockholders Equity [Line Items]
Common stock, shares issued	10.0
Equity Issued in Business Combination [Member] | Common Stock [Member] | STACK [Member]
Stockholders Equity [Line Items]
Units issued for acquisition		23.0