Investment Securities - Summary of Amortized Cost of Securities and Fair Values (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 545,819	$ 588,459
Gross unrealized gains	3,244	3,943
Gross unrealized losses	(5,781)	(10,219)
Available-for-sale securities, at fair value	543,282	582,183
Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	537,966	579,715
Gross unrealized gains	3,243	3,942
Gross unrealized losses	(5,654)	(10,084)
Available-for-sale securities, at fair value	535,555	573,573
Debt Securities \| U.S. Government Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	999	998
Gross unrealized losses	(7)	(13)
Available-for-sale securities, at fair value	992	985
Debt Securities \| Mortgage-backed Securities - Residential
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	423,174	450,874
Gross unrealized gains	586	939
Gross unrealized losses	(4,966)	(7,905)
Available-for-sale securities, at fair value	418,794	443,908
Debt Securities \| Municipals, Tax Exempt
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	104,957	116,034
Gross unrealized gains	2,657	3,003
Gross unrealized losses	(664)	(2,114)
Available-for-sale securities, at fair value	106,950	116,923
Debt Securities \| Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	8,836	11,809
Gross unrealized losses	(17)	(52)
Available-for-sale securities, at fair value	8,819	11,757
Equity Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	7,853	8,744
Gross unrealized gains	1	1
Gross unrealized losses	(127)	(135)
Available-for-sale securities, at fair value	$ 7,727	$ 8,610

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=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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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.

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-Publisher FASB
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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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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
-Section S99
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