Investment Securities - Amortized cost and fair value for available for sale securities - (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Investment securities available for sale
Amortized Cost	$ 1,337,604	$ 1,002,166	$ 968,999
Gross Unrealized Gains	10,477	5,847	20,917
Gross Unrealized Losses	(6,429)	(8,608)	(306)
Fair Value	1,341,652	999,405	989,610
Government-sponsored entities debt
Investment securities available for sale
Amortized Cost	76,508	85,488	102,985
Gross Unrealized Gains	52		107
Gross Unrealized Losses	(608)	(846)
Fair Value	75,952	84,642	103,092
State and municipal obligations
Investment securities available for sale
Amortized Cost	188,720	105,303	118,400
Gross Unrealized Gains	4,680	2,289	5,498
Gross Unrealized Losses	(106)	(190)	(4)
Fair Value	193,294	107,402	123,894
Mortgage-backed securities. issued by Goverment sponsored entities
Investment securities available for sale
Amortized Cost	1,068,718	807,717	743,956
Gross Unrealized Gains	5,195	3,085	14,956
Gross Unrealized Losses	(5,316)	(7,225)	(31)
Fair Value	1,068,597	803,577	758,881
Common Stock
Investment securities available for sale
Amortized Cost	3,658	3,658	3,658
Gross Unrealized Gains	550	473	356
Gross Unrealized Losses	(399)	(347)	(271)
Fair Value	3,809	3,784	3,743
Mortgage-backed securities issued by private label holdings
Investment securities available for sale
Fair Value	$ 0	$ 0	$ 0

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
-Subparagraph (aa)
-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
-Paragraph 1
-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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-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

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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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