Income Taxes (Taxability of Cash Distributions Paid on Common Shares) (Details) - Parent Company - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments, Owned, Federal Income Tax Note
Ordinary income (dollars per share)	$ 3.51	$ 3.66	$ 2.79
Return of capital (dollars per share)	0.21	0.02	0.31
Un-recaptured Section 1250 gain dividends per share	0.12	0.01	0.38
Total (dollars per share)	$ 3.84	$ 3.69	$ 3.48
Ordinary income (percentage per share)	91.40%	99.30%	80.20%
Return of capital (percentage per share)	5.50%	0.60%	8.90%
Un-recaptured Section 1250 gain dividends per share percentage	3.10%	0.10%	10.90%
Total (percentage per share)	100.00%	100.00%	100.00%