Income Taxes and Distributions (Cash Distributions Paid to Common Stockholders for Federal Income Tax Purposes) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Per share:
Ordinary dividend (in USD per share)	$ 1.6389	$ 2.6937	$ 2.1988
Long-term capital gain/(loss) (in USD per share)	1.0611	0.7863	1.1153
Return of capital (in USD per share)	0	0	0.1659
Totals (in USD per share)	2.7000	3.4800	3.4800
Section 199A dividend included in Ordinary dividend (in USD per share)	1.6389	2.6937	2.1988
Gains 1250 per share (in USD per share)	$ 0.3458	$ 0.2835	$ 0.3822