Leases - Summary of Balance Sheet Information Related to Operating Leases (Detail) $ in Thousands	Sep. 30, 2019 USD ($)
Assets:
Operating lease	$ 2,367
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsMember
Liabilities:
Operating lease	$ 2,367
Operating Lease, Liability, Statement of Financial Position [Extensible List]	civb:AccruedExpensesAndOtherLiabilitiesMember