Business Combinations - Summary of Assets Acquired and Liabilities Assumed and Their Initial Fair Value Estimates (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Mar. 11, 2016	Dec. 31, 2015
Liabilities Assumed
Goodwill	$ 66,537		$ 1,822
Retail Branch [Member]
Business Acquisition [Line Items]
Assets Acquired		$ 16,727
Loans		9
Other assets		15
Total assets acquired		16,817
Liabilities Assumed
Deposits		16,957
Other liabilities		138
Total liabilities assumed		17,095
Goodwill		278
Retail Branch [Member] | Fair Value Adjustment [Member]
Business Acquisition [Line Items]
Total assets acquired		66
Liabilities Assumed
Deposits		4
Total liabilities assumed		4
Retail Branch [Member] | Core Deposits [Member]
Business Acquisition [Line Items]
Core deposit intangible		66
Retail Branch [Member] | Core Deposits [Member] | Fair Value Adjustment [Member]
Business Acquisition [Line Items]
Core deposit intangible		66
Book Value [Member] | Retail Branch [Member]
Business Acquisition [Line Items]
Assets Acquired		16,727
Loans		9
Other assets		15
Total assets acquired		16,751
Liabilities Assumed
Deposits		16,953
Other liabilities		138
Total liabilities assumed		$ 17,091