Summary of Significant Accounting Policies - Amortization of Deferred Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Amortization of Deferred Charges	$ 19,142	$ 12,351	$ 8,362
Credit Facility Financing Costs [Member]
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Amortization of Deferred Charges	477	405	228
Leasing Costs [Member]
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Amortization of Deferred Charges	243	161	124
Lease Intangibles (Assets) [Member]
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Amortization of Deferred Charges	22,650	16,060	11,093
Lease Intangibles (Liability) [Member]
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Amortization of Below Market Lease	$ (4,228)	$ (4,275)	$ (3,083)