Securities - Trading Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt and Equity Securities, FV-NI [Line Items]
Trading securities	$ 8,642	$ 7,786
Corporate equity securities
Debt and Equity Securities, FV-NI [Line Items]
Trading securities	6,947	5,828
Mutual funds
Debt and Equity Securities, FV-NI [Line Items]
Trading securities	871	1,058
Certificates of deposit
Debt and Equity Securities, FV-NI [Line Items]
Trading securities	179	268
Corporate notes and bonds
Debt and Equity Securities, FV-NI [Line Items]
Trading securities	594	581
U.S. Gov’t sponsored entities
Debt and Equity Securities, FV-NI [Line Items]
Trading securities	$ 51	$ 51