Subordinated Debentures - Schedule of Issues of Trust Preferred Securities Outstanding and Subordinated Debentures Owed to Trust (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Subordinated Borrowing [Line Items]
Subordinated Debentures Owed to Trust	$ 121,652
Unamortized Discount	(4,249)
Carrying Value of Subordinated Debentures	117,403	$ 64,950	$ 64,950
Trust Preferred Securities of the Trusts	118,000
Ozark II [Member]
Subordinated Borrowing [Line Items]
Subordinated Debentures Owed to Trust	14,433
Unamortized Discount	0
Carrying Value of Subordinated Debentures	14,433
Trust Preferred Securities of the Trusts	$ 14,000
Contractual Interest Rate	3.18%
Ozark III [Member]
Subordinated Borrowing [Line Items]
Subordinated Debentures Owed to Trust	$ 14,434
Unamortized Discount	0
Carrying Value of Subordinated Debentures	14,434
Trust Preferred Securities of the Trusts	$ 14,000
Contractual Interest Rate	3.24%
Ozark IV [Member]
Subordinated Borrowing [Line Items]
Subordinated Debentures Owed to Trust	$ 15,464
Unamortized Discount	0
Carrying Value of Subordinated Debentures	15,464
Trust Preferred Securities of the Trusts	$ 15,000
Contractual Interest Rate	2.50%
Ozark V [Member]
Subordinated Borrowing [Line Items]
Subordinated Debentures Owed to Trust	$ 20,619
Unamortized Discount	0
Carrying Value of Subordinated Debentures	20,619
Trust Preferred Securities of the Trusts	$ 20,000
Contractual Interest Rate	1.89%
Intervest II [Member]
Subordinated Borrowing [Line Items]
Subordinated Debentures Owed to Trust	$ 15,464
Unamortized Discount	(678)
Carrying Value of Subordinated Debentures	14,786
Trust Preferred Securities of the Trusts	$ 15,000
Contractual Interest Rate	3.23%
Intervest III [Member]
Subordinated Borrowing [Line Items]
Subordinated Debentures Owed to Trust	$ 15,464
Unamortized Discount	(785)
Carrying Value of Subordinated Debentures	14,679
Trust Preferred Securities of the Trusts	$ 15,000
Contractual Interest Rate	3.07%
Intervest IV [Member]
Subordinated Borrowing [Line Items]
Subordinated Debentures Owed to Trust	$ 15,464
Unamortized Discount	(1,428)
Carrying Value of Subordinated Debentures	14,036
Trust Preferred Securities of the Trusts	$ 15,000
Contractual Interest Rate	2.68%
Intervest V [Member]
Subordinated Borrowing [Line Items]
Subordinated Debentures Owed to Trust	$ 10,310
Unamortized Discount	(1,358)
Carrying Value of Subordinated Debentures	8,952
Trust Preferred Securities of the Trusts	$ 10,000
Contractual Interest Rate	1.94%