Fair Value of Financial Instruments (Interest Rate Swaps) (Details)	9 Months Ended
	Sep. 30, 2017 USD ($)
Bank of Montreal | Interest Rate Swap Agreements:
Derivatives, Fair Value [Line Items]
Notional Amount	$ 50,000,000
Effective Date	Jan. 29, 2016
Maturity Date	Jan. 31, 2019
Bank of Montreal | Forward Starting Interest Rate Swap Agreements:
Derivatives, Fair Value [Line Items]
Notional Amount	$ 100,000,000
Effective Date	Dec. 29, 2017
Maturity Date	Aug. 31, 2022
Regions Bank | Interest Rate Swap Agreements:
Derivatives, Fair Value [Line Items]
Notional Amount	$ 50,000,000
Effective Date	Feb. 29, 2016
Maturity Date	Jan. 31, 2019
US Bank | Forward Starting Interest Rate Swap Agreements:
Derivatives, Fair Value [Line Items]
Notional Amount	$ 100,000,000
Effective Date	Dec. 29, 2017
Maturity Date	Aug. 31, 2022