Annual report pursuant to Section 13 and 15(d)

Derivative Financial Instruments - Narrative (Details)

v3.8.0.1
Derivative Financial Instruments - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Derivative [Line Items]    
Gains expected to be reclassified to earnings within the next twelve months $ 1.1  
Fair value hedging | Foreign currency forward    
Derivative [Line Items]    
Notional amount $ 20.0 $ 22.2
Cash flow hedging | Foreign currency forward    
Derivative [Line Items]    
Length of derivative hedge (up to) 15 months  
Notional amount $ 40.8 $ 33.2