Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Adjustments to reconcile net income to net cash provided by operating activities
Net income (loss)	$ 39,773,000	$ 31,522,000	$ 12,741,000
Depreciation and amortization	125,159,000	86,589,000	45,471,000
Amortization of deferred financing costs	2,299,000	2,325,000	1,373,000
Amortization of lease inducements and above/below-market lease intangibles	5,083,000	3,906,000	2,577,000
Straight-line rental revenue/expense	(16,202,000)	(16,226,000)	(9,000,000)
Amortization of unsecured bond discount	277,000	0	0
Amortization of above-market assumed debt	(178,000)	(236,000)	(173,000)
Gain on sale of investment properties	(5,874,000)	0	(130,000)
Equity in income of unconsolidated entities	(183,000)	(115,000)	(104,000)
Distribution from unconsolidated entities	210,000	82,000	106,000
Change in fair value of derivatives	150,000	(240,000)	(166,000)
Provision for bad debts	123,000	2,310,000	69,000
Non-cash share compensation	6,695,000	5,672,000	3,798,000
Net change in fair value of contingent consideration	(472,000)	(840,000)	0
Impairment on investment properties	965,000	0	0
Change in operating assets and liabilities:
Tenant receivables	(2,988,000)	(10,058,000)	(2,836,000)
Other assets	(533,000)	(19,230,000)	(2,630,000)
Accounts payable	6,600,000	3,779,000	(56,000)
Accrued expenses and other liabilities	19,567,000	37,957,000	8,312,000
Net cash provided by operating activities	180,471,000	127,197,000	59,352,000
Cash Flows from Investing Activities:
Proceeds on sales of investment properties	20,397,000	0	3,039,000
Acquisition of investment properties, net	(1,268,442,000)	(1,240,438,000)	(752,807,000)
Acquisition of non-controlling interest	(8,469,000)	(4,690,000)	0
Escrowed cash—acquisition deposits/earnest deposits	(1,280,000)	(1,157,000)	2,000,000
Capital expenditures on existing investment properties	(23,243,000)	(11,304,000)	(4,988,000)
Pay down of contingent consideration	(156,000)	(483,000)	(999,000)
Real estate loans receivable	(39,063,000)	(10,207,000)	(22,359,000)
Note receivable	0	0	(20,545,000)
Repayment of real estate loan receivable	4,711,000	11,336,000	0
Repayment of note receivable	16,423,000	4,118,000	0
Leasing commissions	(1,449,000)	(1,034,000)	(579,000)
Lease inducements	(2,067,000)	(8,957,000)	(2,478,000)
Net cash used in investing activities	(1,302,638,000)	(1,262,816,000)	(799,716,000)
Cash Flows from Financing Activities:
Net proceeds from sale of common shares	844,669,000	766,841,000	545,117,000
Proceeds from credit facility borrowings	927,000,000	1,181,000,000	620,000,000
Payment on credit facility borrowings	(1,248,000,000)	(925,000,000)	(363,000,000)
Proceeds from issuance of mortgage debt	61,000,000	39,500,000	0
Proceeds from issuance of senior unsecured notes	743,060,000	225,000,000	0
Principal payments on mortgage debt	(41,503,000)	(10,232,000)	(2,022,000)
Debt issuance costs	(1,589,000)	(4,816,000)	(3,105,000)
Dividends paid - shareholders	(143,108,000)	(104,908,000)	(63,720,000)
Distributions to noncontrolling interest - Operating Partnership	(4,388,000)	(3,162,000)	(3,216,000)
Preferred distributions paid - OP Unit holder	(600,000)	(1,508,000)	(563,000)
Contributions to noncontrolling interest	47,000	0	0
Distributions to noncontrolling interest - partially owned properties	(748,000)	(543,000)	(213,000)
Payments of employee taxes for withheld stock based compensation shares	(2,590,000)	(778,000)	(606,000)
Purchase of Series A Preferred Units	(19,961,000)	(9,756,000)	0
Purchase of OP Units	(3,886,000)	(3,671,000)	(1,088,000)
Net cash provided by financing activities	1,109,403,000	1,147,967,000	727,584,000
Net (decrease) increase in cash and cash equivalents	(12,764,000)	12,348,000	(12,780,000)
Cash and cash equivalents, beginning of period	15,491,000	3,143,000	15,923,000
Cash and cash equivalents, end of period	2,727,000	15,491,000	3,143,000
Supplemental cash flow information:
Supplemental disclosure of cash flow information - interest paid during the year	38,781,000	17,151,000	9,550,000
Other Comprehensive Income (Loss), Net of Tax	244,000	13,708,000	0
Noncash investing and financing activities:
Supplemental disclosure of noncash activity - assumed debt	43,989,000	0	18,690,000
Supplemental disclosure of noncash activity - issuance of OP Units and Series A Preferred Units in connection with acquisitions	44,978,000	6,769,000	40,376,000
Supplemental disclosure of noncash activity - contingent consideration	765,000	156,000	2,718,000
Operating Partnership
Adjustments to reconcile net income to net cash provided by operating activities
Net income (loss)	39,773,000	31,522,000	12,741,000
Depreciation and amortization	125,159,000	86,589,000	45,471,000
Amortization of deferred financing costs	2,299,000	2,325,000	1,373,000
Accelerated amortization of deferred financing costs	0	0	0
Amortization of lease inducements and above/below-market lease intangibles	5,083,000	3,906,000	2,577,000
Straight-line rental revenue/expense	(16,202,000)	(16,226,000)	(9,000,000)
Amortization of unsecured bond discount	277,000	0	0
Amortization of above-market assumed debt	(178,000)	(236,000)	(173,000)
Gain on sale of investment properties	(5,874,000)	0	(130,000)
Equity in income of unconsolidated entities	(183,000)	(115,000)	(104,000)
Distribution from unconsolidated entities	210,000	82,000	106,000
Change in fair value of derivatives	150,000	(240,000)	(166,000)
Provision for bad debts	123,000	2,310,000	69,000
Non-cash share compensation	6,695,000	5,672,000	3,798,000
Net change in fair value of contingent consideration	(472,000)	(840,000)	0
Impairment on investment properties	965,000	0
Change in operating assets and liabilities:
Tenant receivables	(2,988,000)	(10,058,000)	(2,836,000)
Other assets	(533,000)	(19,230,000)	(2,630,000)
Accounts payable	6,600,000	3,779,000	(56,000)
Accrued expenses and other liabilities	19,567,000	37,957,000	8,312,000
Net cash provided by operating activities	180,471,000	127,197,000	59,352,000
Cash Flows from Investing Activities:
Proceeds on sales of investment properties	20,397,000	0	3,039,000
Acquisition of investment properties, net	(1,268,442,000)	(1,240,438,000)	(752,807,000)
Acquisition of non-controlling interest	(8,469,000)	(4,690,000)	0
Escrowed cash—acquisition deposits/earnest deposits	(1,280,000)	(1,157,000)	2,000,000
Capital expenditures on existing investment properties	(23,243,000)	(11,304,000)	(4,988,000)
Pay down of contingent consideration	(156,000)	(483,000)	(999,000)
Real estate loans receivable	(39,063,000)	(10,207,000)	(22,359,000)
Note receivable	0	0	(20,545,000)
Repayment of real estate loan receivable	4,711,000	11,336,000	0
Repayment of note receivable	16,423,000	4,118,000	0
Leasing commissions	(1,449,000)	(1,034,000)	(579,000)
Lease inducements	(2,067,000)	(8,957,000)	(2,478,000)
Net cash used in investing activities	(1,302,638,000)	(1,262,816,000)	(799,716,000)
Cash Flows from Financing Activities:
Net proceeds from sale of common shares	844,669,000	766,841,000	545,117,000
Proceeds from credit facility borrowings	927,000,000	1,181,000,000	620,000,000
Payment on credit facility borrowings	(1,248,000,000)	(925,000,000)	(363,000,000)
Proceeds from issuance of mortgage debt	61,000,000	39,500,000	0
Proceeds from issuance of senior unsecured notes	743,060,000	225,000,000	0
Principal payments on mortgage debt	(41,503,000)	(10,232,000)	(2,022,000)
Debt issuance costs	(1,589,000)	(4,816,000)	(3,105,000)
Dividends paid - shareholders	(143,108,000)	(104,908,000)	(63,720,000)
Distributions to noncontrolling interest - Operating Partnership	(4,388,000)	(3,162,000)	(3,216,000)
Preferred distributions paid - OP Unit holder	(600,000)	(1,508,000)	0
Contributions to noncontrolling interest	47,000	0	0
Distributions to noncontrolling interest - partially owned properties	(748,000)	(543,000)	(213,000)
Payments of employee taxes for withheld stock based compensation shares	(2,590,000)	(778,000)	(606,000)
Purchase of Series A Preferred Units	(19,961,000)	(9,756,000)	(563,000)
Purchase of OP Units	(3,886,000)	(3,671,000)	(1,088,000)
Net cash provided by financing activities	1,109,403,000	1,147,967,000	727,584,000
Net (decrease) increase in cash and cash equivalents	(12,764,000)	12,348,000	(12,780,000)
Cash and cash equivalents, beginning of period	15,491,000	3,143,000	15,923,000
Cash and cash equivalents, end of period	2,727,000	15,491,000	3,143,000
Supplemental cash flow information:
Supplemental disclosure of cash flow information - interest paid during the year	38,781,000	17,151,000	9,550,000
Other Comprehensive Income (Loss), Net of Tax	244,000	13,708,000	0
Noncash investing and financing activities:
Supplemental disclosure of noncash activity - assumed debt	43,989,000	0	18,690,000
Supplemental disclosure of noncash activity - issuance of OP Units and Series A Preferred Units in connection with acquisitions	44,978,000	6,769,000	40,376,000
Supplemental disclosure of noncash activity - contingent consideration	$ 765,000	$ 156,000	$ 2,718,000