v3.8.0.1
Interest Rate Swap (Details) - Designated as Hedging Instrument - Interest Rate Swap
12 Months Ended
Dec. 31, 2017
USD ($)
Derivative [Line Items]  
Unrealized losses expected to be reclassified $ 100,000
Cash Flow Hedge  
Derivative [Line Items]  
Fixed interest rate 1.78%
Notional amount $ 500,000,000
Reduction in notional amount per year $ 100,000,000
Term of contract 5 years
Effective fixed interest rate on long-term debt 4.03%
Hedge ineffectiveness, net (less than) $ 100,000
Interest rate cash flow hedge gain (loss) reclassified into earnings 0
Cash Flow Hedge | Accrued Expenses and Other Liabilities  
Derivative [Line Items]  
Fair value of derivative $ 2,900,000
Cash Flow Hedge | LIBOR  
Derivative [Line Items]  
Basis spread on variable rate 0.75%