Derivatives and Hedging Activities (Narrative) (Details)	3 Months Ended
	Mar. 31, 2020 USD ($) instrument	Dec. 31, 2019 USD ($) instrument	Mar. 31, 2019 USD ($)	Nov. 01, 2019 USD ($)
Derivative [Line Items]
Notional amount				$ 88,700,000
Gain (loss) on non-designated derivatives	$ 16,000		$ (43,000)
Derivative, net liability position, aggregate fair value	44,900,000
Aggregate termination value	$ 44,900,000
Derivatives designated as hedging instruments: | Interest rate “pay-fixed” swaps
Derivative [Line Items]
Number of instruments | instrument	9	9
Number of instruments terminated | instrument		2
Notional amount	$ 578,500,000	$ 578,500,000
Proceeds from sale of interest rate cash flow hedge		2,200,000
Derivatives designated as hedging instruments: | Interest Rate Contract
Derivative [Line Items]
Cash flow hedge reclassification current	1,900,000
Derivatives designated as hedging instruments: | Interest Expense | Interest Rate Contract
Derivative [Line Items]
Cash flow hedge reclassification current	200,000
Cash flow hedge reclassification in next twelve months	9,500,000
Capital One MOB Loan | Interest rate “pay-fixed” swaps
Derivative [Line Items]
Notional amount	53,400,000
Payment for purchase of interest rate cap contract	$ 34,000
Capital One MOB Loan | Derivatives designated as hedging instruments: | Interest rate “pay-fixed” swaps
Derivative [Line Items]
Notional amount		250,000,000.0
Capital One MOB Loan | Derivatives designated as hedging instruments: | Interest Expense | Interest Rate Contract
Derivative [Line Items]
Cash flow hedge reclassification current		$ 2,200,000