Other Borrowings - Summary of Other Borrowings (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Federal Home Loan Bank Borrowings By Year Of Maturity And Applicable Interest Rate [Line Items]
Total other borrowings	$ 147,409	$ 194,572	$ 5,000
Fixed Rate Advance One [Member]
Federal Home Loan Bank Borrowings By Year Of Maturity And Applicable Interest Rate [Line Items]
Advance from Federal Home Loan Bank with a fixed interest rate of 0.16%, due October 24, 2014	25,000
Fixed Rate Advance Two [Member]
Federal Home Loan Bank Borrowings By Year Of Maturity And Applicable Interest Rate [Line Items]
Advance from Federal Home Loan Bank with a fixed interest rate of 0.16%, due October 24, 2014		165,000
Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank Borrowings By Year Of Maturity And Applicable Interest Rate [Line Items]
Daily Rate Credit from Federal Home Loan Bank with a fixed interest rate of 0.36%	75,000
Revolving Credit Facility 1 [Member]
Federal Home Loan Bank Borrowings By Year Of Maturity And Applicable Interest Rate [Line Items]
Advances under revolving credit agreement with a regional bank with interest at 90-day LIBOR plus 3.50% (3.73% at September 30, 2014) due in August 2016, secured by subsidiary bank stock	22,500
Revolving Credit Facility [Member]
Federal Home Loan Bank Borrowings By Year Of Maturity And Applicable Interest Rate [Line Items]
Advances under revolving credit agreement with a regional bank with interest at 90-day LIBOR plus 3.50% (3.73% at September 30, 2014) due in August 2016, secured by subsidiary bank stock		10,000	5,000
Correspondent Bank Advances [Member]
Federal Home Loan Bank Borrowings By Year Of Maturity And Applicable Interest Rate [Line Items]
Advance from correspondent bank with a fixed interest rate of 4.50%, due November 27, 2017, secured by subsidiary bank loan receivable	4,909
Subordinated Debt One [Member]
Federal Home Loan Bank Borrowings By Year Of Maturity And Applicable Interest Rate [Line Items]
Subordinated debt issued by Prosperity Bank due June 2016 with an interest rate of 90-day LIBOR plus 1.60% (1.83% and 1.84% at September 30, 2014 and December 31, 2013)	5,000	5,000
Subordinated Debt Two [Member]
Federal Home Loan Bank Borrowings By Year Of Maturity And Applicable Interest Rate [Line Items]
Subordinated debt issued by Prosperity Bank due June 2016 with an interest rate of 90-day LIBOR plus 1.60% (1.83% and 1.84% at September 30, 2014 and December 31, 2013)	$ 15,000	$ 14,572