Derivative Financial Instruments and Hedging Activities - Outstanding Interest Rate Swaps (Details) - Cash Flow Hedging - Designated as Hedging Instrument	12 Months Ended
	Dec. 31, 2017 USD ($)
August 2015
Derivative [Line Items]
Term	9 years
Notional Amount	$ 170,000
Fixed Rate of Swap	2.20%
Bank Margin on Debt	1.63%
Total Rate	3.83%
August 2015
Derivative [Line Items]
Term	9 years
Notional Amount	$ 180,000
Fixed Rate of Swap	2.35%
Bank Margin on Debt	1.63%
Total Rate	3.98%
April 2016
Derivative [Line Items]
Term	10 years
Notional Amount	$ 100,000
Fixed Rate of Swap	1.60%
Bank Margin on Debt	1.90%
Total Rate	3.50%
April 2016
Derivative [Line Items]
Term	10 years
Notional Amount	$ 100,000
Fixed Rate of Swap	1.60%
Bank Margin on Debt	1.90%
Total Rate	3.50%
July 2016
Derivative [Line Items]
Term	10 years
Notional Amount	$ 100,000
Fixed Rate of Swap	1.26%
Bank Margin on Debt	1.90%
Total Rate	3.16%