XML 129 R93.htm IDEA: XBRL DOCUMENT v3.10.0.1
Derivative Financial Instruments (Details) - USD ($)
9 Months Ended 12 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2016
Dec. 31, 2018
Mar. 12, 2018
Dec. 31, 2017
Oct. 31, 2015
Debt Instrument [Line Items]              
Gain upon settlement of cash flow hedges (less than $0.1 million) $ (500,000) $ (100,000) $ (100,000)        
2015 Interest Rate Swap              
Debt Instrument [Line Items]              
Notional amount             $ 262,500,000
Derivative fixed interest rate             1.46%
2018 Interest Rate Swap              
Debt Instrument [Line Items]              
Notional amount         $ 170,600,000.0    
Amount of hedged item         $ 170,600,000    
Derivative fixed interest rate         2.937%    
2015 Credit Facility              
Debt Instrument [Line Items]              
Amount of hedged item             $ 262,500,000
Credit facility borrowing capacity             $ 350,000,000
2018 Credit Facility              
Debt Instrument [Line Items]              
Notional amount         $ 170,600,000.0    
Derivatives Designated as Hedging Instruments: | Recurring              
Debt Instrument [Line Items]              
Net derivative asset       $ 1,800,000   $ 3,200,000