Annual report pursuant to Section 13 and 15(d)

Fair Value Measurement - Additional Information (Details)

v3.8.0.1
Fair Value Measurement - Additional Information (Details) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Fair Value Disclosures [Abstract]    
Impairment of goodwill $ 0 $ 0