CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net income (loss)	$ 99,438,000	$ (1,614,000)	$ 56,359,000
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Gain on sales of real estate	(127,684,000)	(13,742,000)	(78,365,000)
Depreciation and amortization	69,086,000	47,470,000	48,752,000
Amortization/write-off of deferred financing costs	3,502,000	3,062,000	2,998,000
Change in fair value on derivative instruments included in interest expense	(6,442,000)	(3,948,000)	1,311,000
Net cash received (paid) on derivative settlements	6,842,000	3,832,000	(921,000)
Amortization/write-off of fair market value adjustment of assumed debt	(148,000)	(169,000)	(206,000)
Vesting of stock-based compensation	5,130,000	4,198,000	3,109,000
Casualty losses	3,488,000
Changes in operating assets and liabilities, net of effects of acquisitions:
Operating assets	(350,000)	209,000	1,150,000
Operating liabilities	(1,496,000)	2,445,000	3,319,000
Net cash provided by operating activities	51,366,000	41,743,000	37,506,000
Cash flows from investing activities
Net proceeds from sales of real estate	286,479,000	29,553,000	224,416,000
Prepaid acquisition costs		(7,653,000)
Insurance premiums paid for casualty losses	(600,000)
Insurance proceeds from casualty losses	2,500,000
Additions to real estate investments	(44,159,000)	(26,775,000)	(21,742,000)
Acquisitions of real estate investments	(797,349,000)	(130,373,000)	(197,649,000)
Net cash provided by (used in) investing activities	(553,129,000)	(135,248,000)	5,025,000
Cash flows from financing activities
Mortgage proceeds received	423,149,000	232,252,000	613,213,000
Mortgage payments	(145,821,000)	(148,942,000)	(276,235,000)
Credit facilities proceeds received	255,000,000	55,000,000	25,000,000
Credit facilities payments	(37,000,000)	(85,000,000)	(310,000,000)
Bridge facility proceeds received		30,000,000	65,875,000
Bridge facility payments		(38,597,000)	(87,278,000)
Deferred financing costs paid	(5,120,000)	(2,410,000)	(4,047,000)
Interest rate cap fees paid	(20,000)	(56,000)	(18,000)
Prepayment penalties on extinguished debt	(1,449,000)	(1,706,000)	(2,701,000)
Proceeds from the issuance of common shares through public offering, net of offering costs		84,782,000
Proceeds from the issuance of common shares through at-the-market offering, net of offering costs	69,874,000
Payments for taxes related to net share settlement of stock-based compensation	(751,000)
Repurchase of common stock		(9,672,000)	(2,435,000)
Dividends paid to common stockholders	(28,046,000)	(22,265,000)	(19,258,000)
Distributions to redeemable noncontrolling interests in the Operating Partnership			(69,000)
Contributions from noncontrolling interests			38,000
Distributions to noncontrolling interests			(4,789,000)
Purchase of noncontrolling interests			(51,840,000)
Net cash provided by (used in) financing activities	529,816,000	93,386,000	(54,544,000)
Net increase (decrease) in cash, cash equivalents and restricted cash	28,053,000	(119,000)	(12,013,000)
Cash, cash equivalents and restricted cash, beginning of period	43,129,000	43,248,000	55,261,000
Cash, cash equivalents and restricted cash, end of period	71,182,000	43,129,000	43,248,000
Supplemental Disclosure of Cash Flow Information
Interest paid	41,053,000	30,261,000	25,467,000
Supplemental Disclosure of Noncash Activities
Issuance of operating partnership units for purchase of noncontrolling interests			2,000,000
Capitalized construction costs included in accounts payable and other accrued liabilities	3,776,000	1,715,000	2,263,000
Change in fair value on derivative instruments designated as hedges	(14,625,000)	1,931,000	4,568,000
Other assets acquired from acquisitions	758,000	76,000	325,000
Liabilities assumed from acquisitions	6,608,000	1,382,000	849,000
Fair market value adjustment of assumed debt	980,000
Assumed debt on acquisitions	70,486,000
Write-off of assets due to casualty losses	7,838,000
Write-off of fully amortized in-place leases	8,181,000	1,340,000	9,093,000
Write-off of deferred financing costs	1,419,000	1,412,000	1,003,000
Increase in dividends payable upon vesting of restricted stock units	$ 173,000	$ 336,000	$ 244,000