Loans and Allowance for Loan Losses - Schedule of Details on Loans of Company (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Mortgage loans on real estate
Total mortgage loans on real estate	$ 1,469,944	$ 1,386,308
Agricultural loans	1,573	1,552
Total Loans	1,556,149	1,471,114
Net deferred loan fees	(5,240)	(5,035)
Total loans	1,550,909	1,466,079
Less: Allowance for loan losses	(22,899)	(22,900)	$ (22,572)
Net loans	1,528,010	1,443,179
Residential 1-4 Family [Member]
Mortgage loans on real estate
Total mortgage loans on real estate	350,575	349,631
Total Loans	350,575	349,631
Less: Allowance for loan losses	(4,975)	(5,024)	(5,582)
Multifamily [Member]
Mortgage loans on real estate
Total mortgage loans on real estate	77,088	49,564
Total Loans	77,088	49,564
Less: Allowance for loan losses	(964)	(619)	(172)
Commercial [Member]
Mortgage loans on real estate
Total mortgage loans on real estate	660,335	625,623
Total Loans	660,335	625,623
Less: Allowance for loan losses	(9,905)	(9,986)	(9,578)
Construction and land development [Member]
Mortgage loans on real estate
Total mortgage loans on real estate	294,722	275,319
Total Loans	294,722	275,319
Less: Allowance for loan losses	(4,888)	(5,136)	(5,578)
Farmland [Member]
Mortgage loans on real estate
Total mortgage loans on real estate	32,397	32,114
Total Loans	32,397	32,114
Less: Allowance for loan losses	(665)	(654)	(795)
Second Mortgages [Member]
Mortgage loans on real estate
Total mortgage loans on real estate	8,102	7,551
Total Loans	8,102	7,551
Less: Allowance for loan losses	(114)	(106)	(61)
Equity Lines of Credit [Member]
Mortgage loans on real estate
Total mortgage loans on real estate	46,725	46,506
Total Loans	46,725	46,506
Less: Allowance for loan losses	(573)	(594)	$ (304)
Commercial [Member]
Mortgage loans on real estate
Total Loans	32,216	30,537
Consumer [Member]
Mortgage loans on real estate
Total Loans	43,226	43,467
Consumer [Member] \| Personal [Member]
Mortgage loans on real estate
Total Loans	40,132	40,196
Consumer [Member] \| Credit Cards [Member]
Mortgage loans on real estate
Total Loans	3,094	3,271
Other [Member]
Mortgage loans on real estate
Total Loans	$ 9,190	$ 9,250

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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Total carrying amount of mortgage loans as of the balance sheet date.

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Agriculture loans.

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