Acquisitions - Schedule of Purchase Price of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Sep. 01, 2017
Loans
Goodwill	$ 119,880	$ 119,880
Lafayette Community Bancorp [Member]
Assets
Cash and due from banks			$ 24,846
Investment securities, available for sale			6
Loans
Total loans			134,299
Premises and equipment, net			7,818
FHLB stock			395
Goodwill			15,408
Core deposit intangible			2,085
Interest receivable			338
Other assets			1,649
Total assets purchased			186,844
Common shares issued			30,044
Cash paid			4,421
Total estimated purchase price			34,465
Deposits
Non-interest bearing			34,990
NOW accounts			30,174
Savings and money market			53,663
Certificates of deposit			32,520
Total deposits			151,347
Interest payable			42
Other liabilities			990
Total liabilities assumed			152,379
Lafayette Community Bancorp [Member] | Residential Mortgage [Member]
Loans
Total loans			12,761
Lafayette Community Bancorp [Member] | Commercial [Member]
Loans
Total loans			116,258
Lafayette Community Bancorp [Member] | Consumer [Member]
Loans
Total loans			$ 5,280