Equity and Earnings per Common Share, Non-Controlling Interests, Common Stock ATM Program, Preferred Stock (Details) - USD ($)				1 Months Ended		12 Months Ended
	Jun. 04, 2018	Aug. 17, 2017	Mar. 29, 2017	Aug. 31, 2018	Apr. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Stock Disclosures [Abstract]
Stock issued and sold (in shares)	2,750,000		5,175,000
Issuance of common stock, net of offering costs	$ 53,800,000					$ 69,012,000	$ 81,237,000	$ 125,000
Issuance of preferred stock, net of offering costs						$ 7,722,000	$ 57,917,000	$ 0
Stock issuance expense	$ 265,000		$ 229,000
Series A Preferred Stock [Member]
Class of Stock Disclosures [Abstract]
Number of shares authorized (in shares)						100,000,000	100,000,000
Preferred stock, par value (in dollars per share)		$ 0.01				$ 0.01	$ 0.01
Number of shares undesignated (in shares)						96,200,000
Number of shares designated (in shares)						3,800,000
Number of shares issued (in shares)		2,400,000				2,718,206	2,400,000
Issuance of preferred stock, net of offering costs		$ 58,100,000
Stock issuance expense		$ 193,000
Cash redemption price (in dollars per share)						$ 25.00
Shares issued upon conversion, preferred stock (in shares)						2.62881
Percentage of cash dividends rate		8.20%				8.20%
Liquidation preference per share (in dollars per share)						$ 25.00
Cumulative cash dividends (in dollars per share)						$ 2.05
Series A Preferred Stock [Member] | Preferred Series A ATM Program [Member]
Class of Stock Disclosures [Abstract]
Stock issued and sold (in shares)						318,206
Weighted average price (in dollars per share)						$ 25.37
Stock issuance fee						$ 127,000
Issuance of preferred stock, net of offering costs						$ 8,100,000
Value of shares authorized					$ 35,000,000
Common Stock [Member]
Class of Stock Disclosures [Abstract]
Stock issued and sold (in shares)						3,930,706	5,196,116	6,310
Common Stock [Member] | Common Stock ATM Program [Member]
Class of Stock Disclosures [Abstract]
Common stock value authorized				$ 50,000,000
Stock issued and sold (in shares)						833,593
Weighted average price (in dollars per share)						$ 18.84
Issuance of common stock, net of offering costs						$ 15,700,000
Stock issuance fee						314,000
Stock issuance expense						$ 200,000
LTIP-OP Units [Member] | Operating Partnership [Member]
Noncontrolling Interest in Operating Partnership [Abstract]
Number of LTIP units owned by non-controlling interest holders in Operating Partnership (in shares)						210,067
Percentage of operating partnership						1.30%