Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Net increase (decrease) in shareholders' equity resulting from operations
Net income (loss) attributable to common stockholders	$ 11,122	$ 17,293	$ 12,644	$ 15,408	$ (2,217)	$ 6,661	$ 21,193	$ 21,039	$ 56,467	$ 46,676
Add: Net income (loss) attributable to Convertible Non-controlling Interests									1,305	319
Net income (loss) related to common stockholders and Convertible Non-controlling Interests									57,772	46,995
Dividends Paid:
Dividends									(59,824)	(50,736)
Undistributed (Distributed in excess of) earnings:
Total undistributed (distributed in excess of) earnings									$ (2,052)	$ (3,741)
Weighted average shares outstanding (basic and diluted):
Weighted average shares outstanding (basic and diluted) (in shares)									32,800,224
Basic earnings per share of common stock:
Distributed (in usd per share)									$ 1.81	$ 1.64
Undistributed (Distributed in excess of) (in usd per share)									(0.05)	(0.12)
Basic earnings per common share (in usd per share)									1.76	1.52
Diluted earnings per share of common stock:
Distributed (in usd per share)									1.81	1.64
Undistributed (Distributed in excess of) (usd per share)									(0.05)	(0.12)
Diluted earnings per common share (in usd per share)									$ 1.76	$ 1.52
Net increase (decrease) in equity resulting from operations									$ 3,900	$ 2,900
Common Stock
Net increase (decrease) in shareholders' equity resulting from operations
Net income (loss) attributable to common stockholders										45,922
Dividends Paid:
Dividends									(58,499)	(49,576)
Undistributed (Distributed in excess of) earnings:
Total undistributed (distributed in excess of) earnings									$ (2,032)	$ (3,653)
Weighted average shares outstanding (basic and diluted):
Weighted average shares outstanding (basic and diluted) (in shares)									32,067,768	30,297,401
Long-Term Incentive Plan Units [Member]
Net increase (decrease) in shareholders' equity resulting from operations
Net income (loss) attributable to common stockholders										$ 753
Dividends Paid:
Dividends										(812)
Undistributed (Distributed in excess of) earnings:
Total undistributed (distributed in excess of) earnings										$ (59)
Weighted average shares outstanding (basic and diluted):
Weighted average shares outstanding (basic and diluted) (in shares)										496,962
Non-controlling Interest
Dividends Paid:
Dividends									$ (1,325)	$ (348)
Undistributed (Distributed in excess of) earnings:
Total undistributed (distributed in excess of) earnings									$ (20)	$ (29)
Weighted average shares outstanding (basic and diluted):
Weighted average shares outstanding (basic and diluted) (in shares)									732,456	212,000