Restructuring Charges - Additional Information (Detail) $ in Thousands	12 Months Ended			24 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) Office lease center
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0	$ 1,731	$ 1,642
Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Number of financial centers closed | center				5
Number of administrative offices closed | Office				2
Restructuring charges				$ 3,400
Contract Termination [Member]
Restructuring Cost and Reserve [Line Items]
Number of leases exited | lease				1