Earnings Per Share and Earnings Per Unit - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator for earnings per share - basic:
Net income (loss)		$ 11,156	$ 23,771	$ 12,062	$ 11,332	$ 10,187	$ 12,539	$ 10,331	$ 6,716	$ 58,321	$ 39,773	$ 31,522
Net Income (Loss) Attributable to Noncontrolling Interest [Abstract]
Operating Partnership										(1,576)	(1,136)	(825)
Partially owned properties	[1]									(515)	(491)	(716)
Preferred distributions										(1,340)	(731)	(1,857)
Net income attributable to common shareholders		10,454	22,712	11,303	10,421	9,536	12,018	9,670	6,191	54,890	37,415	28,124
Numerator for earnings per share - diluted:
Net income attributable to common shareholders		$ 10,454	$ 22,712	$ 11,303	$ 10,421	$ 9,536	$ 12,018	$ 9,670	$ 6,191	54,890	37,415	28,124
Operating Partnership net income										1,576	1,136	825
Numerator for earnings per share - diluted										$ 56,466	$ 38,551	$ 28,949
Denominator for earnings per share - basic and diluted:
Weighted average number of shares outstanding - basic (in shares)		182,361,904	182,076,513	182,002,062	181,809,570	179,683,948	177,847,424	155,366,080	138,986,629	182,064,064	163,123,109	126,143,114
Effect of dilutive securities:
Noncontrolling interest - Operating Partnership units										5,329,270	4,839,967	3,692,095
Weighted average number of shares outstanding - diluted (in shares)		187,847,406	187,473,230	187,431,132	187,317,243	185,273,236	183,298,145	161,012,360	142,605,930	187,526,762	168,231,299	130,466,893
Weighted average number of units outstanding - diluted (in shares)				187,431,132
Earnings per share/unit, basic and diluted:
Earnings per share - basic (in dollars per share)		$ 0.06	$ 0.12	$ 0.06	$ 0.06	$ 0.05	$ 0.07	$ 0.06	$ 0.04	$ 0.30	$ 0.23	$ 0.22
Earnings per share - diluted (in dollars per share)		$ 0.06	$ 0.12	$ 0.06	$ 0.06	$ 0.05	$ 0.07	$ 0.06	$ 0.04	$ 0.30	$ 0.23	$ 0.22
Restricted common shares
Effect of dilutive securities:
Effect of dilutive securities, restricted shares and RSUs										99,129	89,497	205,036
Restricted share units
Effect of dilutive securities:
Effect of dilutive securities, restricted shares and RSUs										34,299	178,726	426,648
Operating Partnership
Numerator for earnings per share - basic:
Net income (loss)		$ 11,156	$ 23,771	$ 12,062	$ 11,332	$ 10,187	$ 12,539	$ 10,331	$ 6,716	$ 58,321	$ 39,773	$ 31,522
Net Income (Loss) Attributable to Noncontrolling Interest [Abstract]
Partially owned properties	[1]									(515)	(491)	(716)
Preferred distributions										(1,340)	(731)	(1,857)
Net income attributable to common shareholders		10,730	23,368	11,634	10,734	9,849	12,380	9,984	6,338	56,466	38,551	28,949
Numerator for earnings per unit - basic and diluted										56,466	38,551	28,949
Numerator for earnings per share - diluted:
Net income attributable to common shareholders		$ 10,730	$ 23,368	$ 11,634	$ 10,734	$ 9,849	$ 12,380	$ 9,984	$ 6,338	$ 56,466	$ 38,551	$ 28,949
Denominator for earnings per share - basic and diluted:
Weighted average number of units outstanding - basic (in shares)		187,544,319	187,367,538	187,394,619	187,264,064	185,048,580	183,227,405	160,765,345	142,172,746	187,393,334	167,963,076	129,835,209
Effect of dilutive securities:
Weighted average number of units outstanding - diluted (in shares)		187,847,406	187,473,230		187,317,243	185,273,236	183,298,145	161,012,360	142,605,930	187,526,762	168,231,299	130,466,893
Earnings per share/unit, basic and diluted:
Earnings per unit - basic (in dollars per share)		$ 0.06	$ 0.12	$ 0.06	$ 0.06	$ 0.05	$ 0.07	$ 0.06	$ 0.04	$ 0.30	$ 0.23	$ 0.22
Earnings per unit - diluted (in dollars per share)		$ 0.06	$ 0.12	$ 0.06	$ 0.06	$ 0.05	$ 0.07	$ 0.06	$ 0.04	$ 0.30	$ 0.23	$ 0.22
Operating Partnership | Restricted common shares
Effect of dilutive securities:
Effect of dilutive securities, restricted shares and RSUs										99,129	89,497	205,036
Operating Partnership | Restricted share units
Effect of dilutive securities:
Effect of dilutive securities, restricted shares and RSUs										34,299	178,726	426,648

[1] Includes amounts attributable to redeemable noncontrolling interest.