Business - Additional Information (Detail) $ in Millions	Jun. 30, 2016 FinancialCenters Subsidiary	Feb. 29, 2016 USD ($)
Schedule Of Description Of Company [Line Items]
Number of inactive subsidiaries | Subsidiary	1
Bank operated Business Financial Centers, number	43
Bank operated Commercial Banking Centers, number	8
Bank operated trust office locations, number	3
County Commerce Bank [Member]
Schedule Of Description Of Company [Line Items]
Total assets of merger company | $		$ 253