Annual report pursuant to Section 13 and 15(d)

Derivative Financial Instruments - Additional Information (Details)

v3.8.0.1
Derivative Financial Instruments - Additional Information (Details) - DerivativeInstrument
Dec. 31, 2017
Dec. 31, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]    
Number of open derivative financial instruments 0 0