Leases - Summary of Balance Sheet Information Related to Operating Leases (Detail) $ in Thousands	Mar. 31, 2019 USD ($)
Assets:
Total lease assets	$ 2,133
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsMember
Liabilities:
Total lease liabilities	$ 2,133
Operating Lease, Liability, Statement of Financial Position [Extensible List]	civb:AccruedExpensesAndOtherLiabilitiesMember