Shareholders' Equity (Common Shares) (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended			36 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Shareholders’ Equity [Abstract]
Number of shares authorized for repurchase	35,000,000.0			35,000,000.0
Aggregate amount of shares repurchased pursuant to authorization	23,700,000
Shares repurchased pursuant to authorization				0
Common shares reserved in connection with share-based incentive plan	2,958,817	3,138,618		2,958,817
Common shares reserved for conversion of Convertable Partnership Units	231,978	231,978		231,978
Common shares and restricted shares, dividends	$ 1,398,570	$ 1,396,364	$ 1,393,812
Common shares and restricted shares, dividends per share	$ 8.00	$ 8.00	$ 8.00
Preferred shares, dividends	$ 210,179	$ 216,316	$ 236,535