Investment Securities - Summary of Amortized Cost of Securities and Fair Values (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]
Amortized cost		$ 548,898
Gross unrealized gains		3,067
Gross unrealized losses		(7,973)
Available-for-sale securities, at fair value		543,992
Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 625,672	541,028
Gross unrealized gains	1,641	3,066
Gross unrealized losses	(18,953)	(7,824)
Available-for-sale securities, at fair value	608,360	536,270
Debt Securities \| U.S. Government Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	999	999
Gross unrealized losses	(16)	(13)
Available-for-sale securities, at fair value	983	986
Debt Securities \| Mortgage-backed Securities - Residential
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	494,599	425,557
Gross unrealized gains	169	374
Gross unrealized losses	(16,794)	(7,150)
Available-for-sale securities, at fair value	477,974	418,781
Debt Securities \| Municipals, Tax Exempt
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	122,710	107,127
Gross unrealized gains	1,472	2,692
Gross unrealized losses	(1,935)	(568)
Available-for-sale securities, at fair value	122,247	109,251
Debt Securities \| Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	7,364	7,345
Gross unrealized losses	(208)	(93)
Available-for-sale securities, at fair value	$ 7,156	7,252
Equity and Other Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost		7,870
Gross unrealized gains		1
Gross unrealized losses		(149)
Available-for-sale securities, at fair value		$ 7,722

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
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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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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
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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