Stockholders' Equity Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	1 Months Ended		3 Months Ended	9 Months Ended
	Feb. 28, 2017	Jan. 31, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Jan. 13, 2017
Stockholders' Equity Note [Abstract]
Stock Issued During Period, Shares, New Issues	9,750	65,000
Equity Issuance, Price Per Share						$ 29.00
Proceeds from Issuance of Common Stock			$ 2,100	$ 2,130	$ 8