OTHER BORROWINGS [Parenthetical] (Details)	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Daily Rate Credit From Federal Home Loan Bank [Member]
Other Borrowings [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	0.56%
Revolving Credit Facility [Member]
Other Borrowings [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	8.00%
Debt instrument, maturity period	January 2017
Revolving Credit Facility One [Member]
Other Borrowings [Line Items]
Debt Instrument, Description of Variable Rate Basis	Advances under revolving credit agreement with a regional bank with interest at 90-day LIBOR plus 3.50% (4.34% at September 30, 2016, 3.92% at December 31, 2015, and 3.78% at September 30, 2015) due in August 2017, secured by subsidiary bank stock
Debt Instrument, Interest Rate, Effective Percentage	4.34%	3.92%	3.78%
Debt instrument, maturity period	August 2017
Correspondent Bank Advances [Member]
Other Borrowings [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	4.25%
Debt instrument, maturity period	October 15, 2019
Fixed Rate Advance One [Member]
Other Borrowings [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	1.40%
Debt instrument, maturity period	January 9, 2017
Fixed Rate Advance Two [Member]
Other Borrowings [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	1.23%
Debt instrument, maturity period	May 30, 2017
Subordinated Debt [Member]
Other Borrowings [Line Items]
Debt Instrument, Description of Variable Rate Basis	Subordinated debt issued by The Prosperity Banking Company due September 2016 with an interest rate of 90-day LIBOR plus 1.75% (2.28% at December 31, 2015 and 2.09% at September 30, 2015)
Debt Instrument, Interest Rate, Effective Percentage		2.28%	2.09%
Fixed Rate Advance [Member]
Other Borrowings [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	0.40%
Debt instrument, maturity period	October 14, 2016