Shareholders' Equity - Preferred shares (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		1 Months Ended			4 Months Ended
	Jan. 01, 2018	Jun. 30, 2021	Nov. 30, 2017	Aug. 31, 2017	Nov. 30, 2017	Dec. 31, 2021
Class of Stock [Line Items]
Preferred shares, par value per share						$ 0.01
Series C Preferred Shares
Class of Stock [Line Items]
Preferred shares, dividend rate (as a percent)	6.75%
Series E preferred shares
Class of Stock [Line Items]
Preferred shares, dividend rate (as a percent)	5.25%
Preferred shares, redemption price per share	$ 25
Series F Preferred Shares
Class of Stock [Line Items]
Preferred shares issued			$ 100	$ 230	$ 330
Preferred shares, dividend rate (as a percent)					5.45%
Preferred shares, par value per share			$ 0.01		$ 0.01
Liquidation preference per share			25,000		25,000
Preferred shares, redemption price per share			$ 25,000		$ 25,000
Series F depositary share equivalent
Class of Stock [Line Items]
Preference shares, number of shares issued			13.2		13.2
Proportionate interest of preference shares, per depositary share			0.10%		0.10%
Liquidation preference per share			$ 25		$ 25
Preferred shares, redemption price per share			$ 25		$ 25
Series G Preferred Stock
Class of Stock [Line Items]
Preferred shares issued		$ 500
Preferred shares, dividend rate (as a percent)		4.55%
Preferred shares, par value per share		$ 0.01
Liquidation preference per share		25,000
Preferred shares, redemption price per share		$ 25,000
Series G depositary share equivalent
Class of Stock [Line Items]
Preference shares, number of shares issued		20.0
Proportionate interest of preference shares, per depositary share		0.10%
Liquidation preference per share		$ 25
Preferred shares, redemption price per share		$ 25