Quarterly Data (Unaudited) - 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
Quarterly Financial Data [Line Items]
Revenues	$ 105,311	$ 105,028	$ 106,989	$ 105,223	$ 97,320	$ 92,999	$ 76,599	$ 76,666	$ 422,551	$ 343,584	$ 241,034
Net income	11,156	23,771	12,062	11,332	10,187	12,539	10,331	6,716	58,321	39,773	31,522
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
Earnings per share – basic:
Net income available to common shareholders - 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
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
Earnings per share – diluted:
Net income available to common shareholders (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
Weighted average common shares - 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 common units - diluted (in shares)			187,431,132
Operating Partnership
Quarterly Financial Data [Line Items]
Revenues	$ 105,311	$ 105,028	$ 106,989	$ 105,223	$ 97,320	$ 92,999	$ 76,599	$ 76,666	$ 422,551	$ 343,584	$ 241,034
Net income	11,156	23,771	12,062	11,332	10,187	12,539	10,331	6,716	58,321	39,773	31,522
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
Earnings per share – basic:
Net income available to common unitholders - 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
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
Earnings per share – diluted:
Net income available to common unitholders - 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
Weighted average common units - 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