Investments (Details Textual) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities Pledged As Collateral Amortized Cost	$ 354,700,000
Payments to Acquire Investments	(196,600,000)		(140,000,000)
Proceeds from Sale of Available-for-sale Securities	144,945,000		142,041,000
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	2,364,000	5,559,000	10,172,000
Federal Home Loan Bank stock, at cost	28,905,000	40,609,000
Net change in FLHB Stock	11,704,000		2,939,000
Redemptions of FHLB stock	15,600,000
Purchases of FHLB Stock	(3,900,000)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Reclassification Adjustments, Net of Tax	4,258,000	5,559,000	12,928,000
Government agency and government-sponsored enterprise pass through securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sale of Available-for-sale Securities	60,300,000		137,300,000
Available-for-sale Securities, Gross Realized Gains			4,800,000
Government agency and government-sponsored enterprise pass through securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains	2,600,000
Texas Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sale of Available-for-sale Securities	13,900,000
Available-for-sale Securities, Gross Realized Gains	883,000
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sale of Available-for-sale Securities	67,500,000
Available-for-sale Securities, Gross Realized Losses	$ (232,000)