Other Noninterest Expense - Summary of Other Noninterest Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Other Income and Expenses [Abstract]
Lending and other client related processing costs	$ 5,698	$ 6,935	$ 16,301	$ 18,806
Data processing services	2,740	2,244	7,934	7,254
Telephone	2,269	2,518	7,025	7,892
Dues and publications	1,387	883	3,081	2,355
Postage and supplies	652	612	2,133	2,013
Other	5,393	4,872	15,171	16,350
Total other noninterest expense	$ 18,139	$ 18,064	$ 51,645	$ 54,670