Financial Instruments and Fair Values - Summary of the Terms of Agreements and the Fair Value of Derivative Financial Instruments (Details) - Designated as Hedging Instrument - Cash Flow Hedging - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Asset	$ 9,944,000	$ 0
Liability	0	(436,000)
LIBOR | Interest Rate Swap, One Month LIBOR, 2.1485%
Derivatives, Fair Value [Line Items]
Notional Amount	$ 265,000,000
Pay Rate (as a percent)	2.1485%
Asset	$ 7,300,000	0
Liability	0	(436,000)
LIBOR | Interest Rate Swap, Three Month LIBOR, 2.9580%
Derivatives, Fair Value [Line Items]
Notional Amount	$ 125,000,000
Pay Rate (as a percent)	2.958%
Asset	$ 1,316,000	0
Liability	0	0
LIBOR | Interest Rate Swap, Three Month LIBOR, 2.9580%
Derivatives, Fair Value [Line Items]
Notional Amount	$ 125,000,000
Pay Rate (as a percent)	2.958%
Asset	$ 1,328,000	0
Liability	$ 0	$ 0