Investment Securities - Amortized cost and fair value for available for sale securities - (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Investment securities available for sale
Amortized Cost	$ 909,150	$ 1,005,359	$ 873,981
Gross Unrealized Gains	16,663	8,727	13,715
Gross Unrealized Losses	(439)	(4,545)	(1,898)
Fair Value	925,374	1,009,541	885,798
Government-sponsored entities debt
Investment securities available for sale
Amortized Cost	62,996	163,577	123,926
Gross Unrealized Gains	20	39	188
Gross Unrealized Losses	(36)	(1,109)	(320)
Fair Value	62,980	162,507	123,794
State and municipal obligations
Investment securities available for sale
Amortized Cost	112,797	127,293	130,553
Gross Unrealized Gains	4,542	4,185	3,946
Gross Unrealized Losses	(15)	(114)	(161)
Fair Value	117,324	131,364	134,338
Mortgage-backed securities.
Investment securities available for sale
Amortized Cost	729,699	710,816	616,341
Gross Unrealized Gains	11,721	4,063	9,170
Gross Unrealized Losses	(143)	(3,030)	(438)
Fair Value	741,277	711,849	625,073
Common Stock
Investment securities available for sale
Amortized Cost	3,658	3,673	3,161
Gross Unrealized Gains	380	440	411
Gross Unrealized Losses	(245)	(292)	(979)
Fair Value	$ 3,793	$ 3,821	$ 2,593

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
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
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-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

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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
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
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