Quarterly report pursuant to Section 13 or 15(d)

Soft Dollar Arrangements - Additional Information (Detail)

v3.8.0.1
Soft Dollar Arrangements - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Soft Dollar Arrangements [Abstract]        
Soft dollar credits $ 178 $ 199 $ 534 $ 597