Investment Securities - Securities with gross unrealized losses - (Details) $ in Thousands	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($)
Investment Securities
Number of securities with gross unrealized loss \| item	129
Securities Available for Sale, Gross Unrealized Losses
Less Than Twelve Months	$ 8,184	$ 3,326
Twelve Months or More	424	1,219
Securities Available for Sale, Fair Value
Less Than Twelve Months	688,376	439,359
Twelve Months or More	3,453	45,470
Government-sponsored entities debt
Securities Available for Sale, Gross Unrealized Losses
Less Than Twelve Months	846	717
Twelve Months or More		392
Securities Available for Sale, Fair Value
Less Than Twelve Months	84,642	88,224
Twelve Months or More		17,598
State and municipal obligations
Securities Available for Sale, Gross Unrealized Losses
Less Than Twelve Months	190	9
Twelve Months or More		105
Securities Available for Sale, Fair Value
Less Than Twelve Months	11,506	3,755
Twelve Months or More		2,650
Mortgage-backed securities.
Securities Available for Sale, Gross Unrealized Losses
Less Than Twelve Months	7,148	2,600
Twelve Months or More	77	430
Securities Available for Sale, Fair Value
Less Than Twelve Months	592,228	347,380
Twelve Months or More	2,058	23,772
Common Stock
Securities Available for Sale, Gross Unrealized Losses
Twelve Months or More	347	292
Securities Available for Sale, Fair Value
Twelve Months or More	$ 1,395	$ 1,450

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27337-111563

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months.

+ References

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- Definition

This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27290-111563

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27337-111563

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Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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