Derivatives - Fair Value Measurements on Recurring Basis (Details) $ in Thousands	Jun. 30, 2018 USD ($)
2014 Swaps
Derivatives, Fair Value [Line Items]
Hedging Instrument, Asset, Fair Value	$ 1,862
2014 Swaps | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Derivatives, Fair Value [Line Items]
Hedging Instrument, Asset, Fair Value	0
2014 Swaps | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Derivatives, Fair Value [Line Items]
Hedging Instrument, Asset, Fair Value	1,862
2014 Swaps | Fair Value, Measurements, Recurring | Unobservable Inputs (Level 3)
Derivatives, Fair Value [Line Items]
Hedging Instrument, Asset, Fair Value	0
2015 Swaps
Derivatives, Fair Value [Line Items]
Hedging Instrument, Asset, Fair Value	9,774
2015 Swaps | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Derivatives, Fair Value [Line Items]
Hedging Instrument, Asset, Fair Value	0
2015 Swaps | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Derivatives, Fair Value [Line Items]
Hedging Instrument, Asset, Fair Value	9,774
2015 Swaps | Fair Value, Measurements, Recurring | Unobservable Inputs (Level 3)
Derivatives, Fair Value [Line Items]
Hedging Instrument, Asset, Fair Value	$ 0