Acquisition - Amounts of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	$ 1,068,828	$ 1,190,717
Carrying amount, net of allowance of $389	1,051,943	1,170,196
Heartland Bancshares Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	60,294	98,903
Carrying amount, net of allowance of $389	59,905	98,903
Commercial [Member] | Heartland Bancshares Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	37,048	63,952
Real Estate [Member] | Heartland Bancshares Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	11,761	18,662
Consumer [Member] | Heartland Bancshares Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	$ 11,485	$ 16,289