Quarterly Data (Unaudited) - Quarterly Per Share Information (Details) - $ / shares shares in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Weighted average common shares outstanding—basic	925	925	924	923	921	913	863	862	924	890	860
Net Income per Basic Share	$ 0.22	$ 0.53	$ 0.29	$ 0.19	$ 0.34	$ 0.69	$ 0.74	$ 0.80
Weighted average common shares outstanding—diluted	928	927	926	925	924	915	866	867	927	893	864
Net Income per Diluted Share	$ 0.22	$ 0.53	$ 0.29	$ 0.19	$ 0.33	$ 0.69	$ 0.74	$ 0.80	$ 1.22	$ 2.54	$ 1.88