Derivative Financial Instruments - Summary of Information Related to Number of and Notional Amount of Interest Rate Related Derivative Instruments (Details) - Interest Rate Swaps and Collars - Designated as Hedging Instrument - Cash Flow Hedges	Jun. 30, 2018 USD ($) DerivativeInstrument	Dec. 31, 2017 USD ($) DerivativeInstrument
Derivative [Line Items]
Number of Instruments | DerivativeInstrument	14	14
Notional Amount | $	$ 220,000,000	$ 220,000,000