Equity Schedule of Equity by Type (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Class of Stock [Line Items]
Proceeds from Issuance of Common Stock			$ 841	$ 464
Common Stock [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues	0	5	8	4
Proceeds from Issuance of Common Stock	$ 0