Quarterly Data (Unaudited) - Quarterly Per Share Information (Details) - $ / shares shares in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Data [Abstract]
Weighted average common shares outstanding—basic	921	913	863	862	861	861	860	858	890	860	856
Earnings Per Share, Basic	$ 0.34	$ 0.69	$ 0.74	$ 0.80	$ 0.02	$ 1.15	$ 0.61	$ 0.10
Weighted average common shares outstanding—diluted	924	915	866	867	868	863	864	861	893	864	860
Earnings Per Share, Diluted	$ 0.33	$ 0.69	$ 0.74	$ 0.80	$ 0.02	$ 1.15	$ 0.60	$ 0.10	$ 2.54	$ 1.88	$ 2.00