Investment Securities, Available-for-sale Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Amortized cost and fair value of the securities available for sale [Abstract]
Amortized Cost	$ 669,945	$ 682,913
Gross Unrealized Gains	1,563	1,149
Gross Unrealized Losses	4,657	7,303
Fair Value	666,851us-gaap_AvailableForSaleSecurities	676,759us-gaap_AvailableForSaleSecurities
U. S. government sponsored enterprises [Member]
Amortized cost and fair value of the securities available for sale [Abstract]
Amortized Cost	108,421	78,420
Gross Unrealized Gains	67	2
Gross Unrealized Losses	240	622
Fair Value	108,248	77,800
State and political subdivisions [Member]
Amortized cost and fair value of the securities available for sale [Abstract]
Amortized Cost	1,939	2,232
Gross Unrealized Gains	35	39
Gross Unrealized Losses	0	0
Fair Value	1,974	2,271
Mortgage-backed securities and collateralized mortgage obligations-residential [Member]
Amortized cost and fair value of the securities available for sale [Abstract]
Amortized Cost	446,068	486,107
Gross Unrealized Gains	1,461	1,108
Gross Unrealized Losses	2,256	3,655
Fair Value	445,273	483,560
Corporate bonds [Member]
Amortized cost and fair value of the securities available for sale [Abstract]
Amortized Cost	1,500	1,500
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	1,500	1,500
Small Business Administration-guaranteed participation securities [Member]
Amortized cost and fair value of the securities available for sale [Abstract]
Amortized Cost	100,704	103,273
Gross Unrealized Gains	0	0
Gross Unrealized Losses	2,036	2,777
Fair Value	98,668	100,496
Mortgage-backed securities and collateralized mortgage obligations-Commercial [Member]
Amortized cost and fair value of the securities available for sale [Abstract]
Amortized Cost	10,628	10,696
Gross Unrealized Gains	0	0
Gross Unrealized Losses	125	249
Fair Value	10,503	10,447
Other [Member]
Amortized cost and fair value of the securities available for sale [Abstract]
Amortized Cost	650	650
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	650	650
Debt securities [Member]
Amortized cost and fair value of the securities available for sale [Abstract]
Amortized Cost	669,910	682,878
Gross Unrealized Gains	1,563	1,149
Gross Unrealized Losses	4,657	7,303
Fair Value	666,816	676,724
Equity securities [Member]
Amortized cost and fair value of the securities available for sale [Abstract]
Amortized Cost	35	35
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 35	$ 35

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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-Publisher FASB

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

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