Equity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Dividends Payable [Line Items]
Common Stock, Dividends, Per Share, Cash Paid	[1]	$ 1.125
Preferred Stock, Dividends Per Share, Declared		$ 17.1875	$ 17.1875	$ 17.1875
Dividends, Common Stock, Cash	[1]	$ 468
Dividends, Preferred Stock, Cash		$ 28	$ 28
Common stock repurchased during period, shares		0.3
Purchases of Common Stock		$ (42)		$ (33)
Availability Under ATM		$ 750
Common Stock [Member]
Dividends Payable [Line Items]
Dividends Payable, Date Declared	[1]	Feb. 21, 2019
Dividends Payable, Date of Record	[1]	Mar. 15, 2019
Dividends Payable, Date to be Paid	[1]	Mar. 29, 2019
Preferred Stock [Member]
Dividends Payable [Line Items]
Dividends Payable, Date Declared		Mar. 19, 2019	Dec. 11, 2018
Dividends Payable, Date of Record		Apr. 15, 2019	Jan. 15, 2019
Dividends Payable, Date to be Paid		May 01, 2019	Feb. 01, 2019

[1] Inclusive of dividends accrued for holders of unvested restricted stock units, which will be paid when and if the restricted stock units vest.