Capital Actions (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Equity [Abstract]
Number of shares issued in public offering	350,000
Class of Stock [Line Items]
Proceeds from issuance of shares in public offering	$ 346
Preferred stock, liquidation preference per share (in dollars per share)		$ 25,000	$ 25,000
Series L Preferred Stock
Class of Stock [Line Items]
Preferred stock, issued (in shares)	14,000
Preferred stock, dividend rate	4.50%
Preferred stock, liquidation preference per share (in dollars per share)	$ 25,000
Preferred stock, redemption, percentage	100.00%
Series L Preferred Stock | Treasury Rate
Class of Stock [Line Items]
Preferred stock, basis spread on variable rate (as a percent)	4.215%