Investment Securities - Unrealized Gain (Loss) on Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	$ 128,397	$ 120,325
Less than 12 months, unrealized losses	1,288	513
More than 12 months, fair value	124,912	124,903
More than 12 months, unrealized losses	871	869
Fair Value	253,309	245,228
Unrealized Losses	2,159	1,382
U.S. Treasury and government sponsored entities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	120,700	116,331
Less than 12 months, unrealized losses	1,269	496
More than 12 months, fair value	122,618	122,605
More than 12 months, unrealized losses	842	840
Fair Value	243,318	238,936
Unrealized Losses	2,111	1,336
Collateralized loan obligations
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	3,000
Less than 12 months, unrealized losses	1
More than 12 months, fair value	0
More than 12 months, unrealized losses	0
Fair Value	3,000
Unrealized Losses	1
Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	4,697	3,994
Less than 12 months, unrealized losses	18	17
More than 12 months, fair value	2,294	2,298
More than 12 months, unrealized losses	29	29
Fair Value	6,991	6,292
Unrealized Losses	$ 47	$ 46

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=82897076&loc=d3e27290-111563

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

+ 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=82897076&loc=d3e27337-111563

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-Publisher FASB
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