Consolidated Statements of Operations - USD ($)		3 Months Ended									6 Months Ended			9 Months Ended			12 Months Ended
		Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Revenues:
Rental revenues																	$ 186,301,000		$ 103,974,000		$ 46,397,000
Expense recoveries																	45,875,000		21,587,000		5,871,000
Interest income on real estate loans and other																	8,858,000		3,880,000		1,066,000
Total revenues		$ 70,010,000	$ 53,216,000	$ 44,134,000	$ 34,870,000	$ 29,683,000	$ 24,484,000										241,034,000		129,441,000		53,334,000
Expenses:
Interest expense																	23,864,000		10,636,000		6,907,000
General and administrative																	18,397,000		14,908,000		11,440,000
Operating expenses																	65,999,000		31,026,000		10,154,000
Depreciation and amortization																	86,589,000		45,471,000		16,731,000
Acquisition expenses																	14,778,000		14,893,000		10,897,000
Impairment loss																	0		0		1,750,000
Total expenses																	209,627,000		116,934,000		57,879,000
Income (loss) before equity in income of unconsolidated entities and gain on sale of investment properties:		10,267,000	7,158,000	5,392,000	3,812,000	3,271,000	(459,000)										31,407,000		12,507,000		(4,545,000)
Equity in income of unconsolidated entities																	115,000		104,000		95,000
Gain on sale of investment properties										$ 0							0		130,000		32,000
Net income (loss)		10,294,000	7,184,000	5,424,000	3,983,000	3,297,000	(448,000)										31,522,000		12,741,000		(4,418,000)
Net (income) loss attributable to noncontrolling interests:
Operating Partnership																	(825,000)		(576,000)		695,000
Partially owned properties (1)	[1]																(716,000)		(377,000)		(314,000)
Net income (loss) attributable to controlling interest																	29,981,000		11,788,000		(4,037,000)
Preferred distributions																	(1,857,000)		(1,189,000)		0
Net income (loss) attributable to common shareholders		$ 9,427,000	$ 6,486,000	$ 4,386,000	$ 3,404,000	$ 2,571,000	$ (522,000)										$ 28,124,000		$ 10,599,000		$ (4,037,000)
Net income (loss) per share:
Earnings per share - basic (in dollars per share)		$ 0.07	$ 0.05	$ 0.04	$ 0.05	$ 0.04	$ (0.01)										$ 0.22		$ 0.15		$ (0.12)
Earnings per share - diluted (in dollars per share)		$ 0.07	$ 0.05	$ 0.04	$ 0.05	$ 0.04	$ (0.01)										$ 0.22		$ 0.15		$ (0.12)
Weighted average common shares:
Weighted average common shares - basic (in shares)		134,608,396	131,481,329	102,704,008	71,034,747	70,376,959	65,649,478														33,063,093
Weighted average common shares - diluted (in shares)		138,880,787	135,944,722	107,148,380	75,104,821	74,267,284	65,649,478										130,466,893		76,792,073		33,063,093
Dividends and distributions declared per common share and OP unit (in dollars per share)																	$ 0.9		$ 0.9		$ 0.9
Earnings per unit:
Earnings per unit - basic (in dollars per share)																	0.22		0.15		(0.12)
Earnings per unit - diluted (in dollars per share)																	$ 0.22		$ 0.15		$ (0.12)
Weighted average common units - basic (in shares)																	129,835,209		76,459,218		36,881,712
Weighted average common units - diluted (in shares)																	130,466,893		76,792,073		36,881,712
Net income (loss) attributable to redeemable noncontrolling interest																	$ 100,000
Operating Partnership
Revenues:
Rental revenues		$ 53,327,000	$ 42,196,000	$ 34,855,000	$ 28,145,000	$ 23,625,000	$ 20,341,000	$ 12,506,000	$ 10,241,000	6,808,000	$ 77,051,000	$ 43,966,000	$ 17,049,000	$ 130,378,000	$ 72,111,000	$ 29,555,000	186,301,000		$ 103,974,000		$ 46,397,000
Expense recoveries		14,361,000	9,552,000	7,903,000	5,821,000	4,908,000	3,536,000	1,355,000	1,020,000	1,070,000	17,455,000	8,444,000	2,090,000	31,816,000	14,265,000	3,445,000	45,875,000		21,587,000		5,871,000
Interest income on real estate loans and other		2,322,000	1,468,000	1,376,000	904,000	1,150,000	607,000	300,000	186,000	154,000	2,844,000	1,757,000	340,000	5,166,000	2,661,000	640,000	8,858,000		3,880,000		1,066,000
Total revenues		70,010,000	53,216,000	44,134,000	34,870,000	29,683,000	24,484,000	14,161,000	11,447,000	8,032,000	97,350,000	54,167,000	19,479,000	167,360,000	89,037,000	33,640,000	241,034,000		129,441,000		53,334,000
Expenses:
Interest expense		7,300,000	4,279,000	4,197,000	3,341,000	2,193,000	1,710,000	1,911,000	1,657,000	1,281,000	8,476,000	3,903,000	2,938,000	15,776,000	7,244,000	4,849,000	23,864,000		10,636,000		6,907,000
General and administrative		4,917,000	4,926,000	4,121,000	4,018,000	3,989,000	3,352,000	4,445,000	2,408,000	2,014,000	9,047,000	7,341,000	4,422,000	13,964,000	11,359,000	8,867,000	18,397,000		14,908,000		11,440,000
Operating expenses		19,159,000	13,798,000	11,037,000	7,966,000	7,304,000	5,709,000	2,531,000	2,227,000	1,609,000	24,835,000	13,013,000	3,836,000	43,994,000	20,979,000	6,367,000	65,999,000		31,026,000		10,154,000
Depreciation and amortization		23,969,000	19,799,000	16,010,000	12,476,000	10,351,000	8,240,000	4,413,000	3,736,000	2,416,000	35,809,000	18,591,000	6,152,000	59,778,000	31,067,000	10,565,000	86,589,000		45,471,000		16,731,000
Acquisition expenses		4,398,000	3,256,000	3,377,000	3,257,000	2,575,000	5,932,000	2,922,000	2,045,000	4,287,000	6,633,000	8,507,000	6,332,000	11,031,000	11,764,000	9,254,000	14,778,000		14,893,000		10,897,000
Impairment loss					0			250,000							0	250,000	0		0		1,750,000
Total expenses		59,743,000	46,058,000	38,742,000	31,058,000	26,412,000	24,943,000	16,472,000	12,073,000	11,607,000	84,800,000	51,355,000	23,680,000	144,543,000	82,413,000	40,152,000	209,627,000		116,934,000		57,879,000
Income (loss) before equity in income of unconsolidated entities and gain on sale of investment properties:		10,267,000	7,158,000	5,392,000	3,812,000	3,271,000	(459,000)	(2,311,000)	(626,000)	(3,575,000)	12,550,000	2,812,000	(4,201,000)	22,817,000	6,624,000	(6,512,000)	31,407,000		12,507,000		(4,545,000)
Equity in income of unconsolidated entities		27,000	26,000	32,000	26,000	26,000	26,000	26,000	26,000	17,000	58,000	52,000	43,000	85,000	78,000	69,000	115,000		104,000		95,000
Gain on sale of investment properties		0	0	0	145,000	0	(15,000)	34,000	0	0	0	(15,000)	0	0	130,000	34,000	0		130,000		32,000
Net income (loss)		10,294,000	7,184,000	5,424,000	3,983,000	3,297,000	(448,000)	(2,251,000)	(600,000)	(3,558,000)	12,608,000	2,849,000	(4,158,000)	22,902,000	6,832,000	(6,409,000)	31,522,000		12,741,000		(4,418,000)
Net (income) loss attributable to noncontrolling interests:
Partially owned properties (1)		(176,000)	(60,000)	(317,000)	(79,000)	(144,000)	(32,000)	(76,000)	(84,000)	(66,000)	(377,000)	(176,000)	(150,000)	(553,000)	(255,000)	(226,000)	(716,000)	[1]	(377,000)	[1]	(314,000)	[1]
Net income (loss) attributable to controlling interest		10,118,000	7,124,000	5,107,000	3,904,000	3,153,000	(480,000)	(2,327,000)	(684,000)	(3,624,000)	12,231,000	2,673,000	(4,308,000)	22,349,000	6,577,000	(6,635,000)	30,806,000		12,364,000		(4,732,000)
Preferred distributions		(436,000)	(437,000)	(548,000)	(300,000)	(425,000)	(66,000)	0	0	0	(985,000)	(491,000)	0	(1,421,000)	(791,000)	0	(1,857,000)		(1,189,000)		0
Net loss attributable to common unitholders							(546,000)			$ (3,624,000)
Net income (loss) attributable to common shareholders		$ 9,682,000	$ 6,687,000	$ 4,559,000	$ 3,604,000	$ 2,728,000	$ (546,000)	$ (2,327,000)	$ (684,000)		$ 11,246,000	$ 2,182,000	$ (4,308,000)	$ 20,928,000	$ 5,786,000	$ (6,635,000)	$ 28,949,000		$ 11,175,000		$ (4,732,000)
Net income (loss) per share:
Earnings per share - basic (in dollars per share)																	$ 0.22		$ 0.15		$ (0.12)
Earnings per share - diluted (in dollars per share)																	$ 0.22		$ 0.15		$ (0.12)
Weighted average common shares:
Weighted average common shares - basic (in shares)																	126,143,114		72,750,724		33,063,093
Weighted average common shares - diluted (in shares)																	130,466,893		76,792,073		33,063,093
Earnings per unit:
Earnings per unit - basic (in dollars per share)		$ 0.07	$ 0.05	$ 0.04	$ 0.05	$ 0.04	$ (0.01)	$ (0.06)	$ (0.02)		$ 0.09	$ 0.03	$ (0.15)	$ 0.17	$ 0.08	$ (0.21)	$ 0.22		$ 0.15		$ (0.12)
Earnings per unit - diluted (in dollars per share)		$ 0.07	$ 0.05	$ 0.04	$ 0.05	$ 0.04	$ (0.01)	$ (0.06)	$ (0.02)		$ 0.09	$ 0.03	$ (0.15)	$ 0.16	$ 0.08	$ (0.21)	$ 0.22		$ 0.15		$ (0.12)
Weighted average common units - basic (in shares)		138,227,384	135,351,672	106,550,467	74,864,677	74,075,323	69,146,712	40,898,015	29,962,046		120,951,069	71,624,633	27,493,474	126,751,876	72,716,516	32,010,755	129,835,209		76,459,218		36,881,712
Weighted average common units - diluted (in shares)		138,880,787	135,944,722	107,148,380	75,104,821	74,267,284	69,146,712	40,898,015	29,962,046		121,575,247	71,862,249	27,493,474	127,395,989	73,040,846	32,010,755	130,466,893		76,792,073		36,881,712
Distributions declared per common OP Unit (in dollars per share)		$ 0.225	$ 0.225	$ 0.225	$ 0.225	$ 0.225	$ 0.225	$ 0.225	$ 0.225	$ 0.225	$ 0.45	$ 0.45	$ 0.45	$ 0.675	$ 0.675	$ 0.675	$ 0.9		$ 0.9		$ 0.9
Net loss per unit (in dollars per share)							$ (0.01)			$ (0.15)
Weighted average common units (in shares)							69,146,712			24,997,474
Net income (loss) attributable to redeemable noncontrolling interest																	$ 100,000

[1] Includes $0.1 million of net income attributable to redeemable noncontrolling interests for the year ended December 31, 2016. No such adjustments are required for the years ended December 31, 2015 and 2014.