Investment Securities - Summary of Amortized Cost of Securities and Fair Values (Details) - USD ($) $ in Thousands	Sep. 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	$ 628,910	541,028
Gross unrealized gains	1,008	3,066
Gross unrealized losses	(23,417)	(7,824)
Available-for-sale securities, at fair value	606,501	536,270
Debt Securities \| U.S. Government Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	999	999
Gross unrealized losses	(15)	(13)
Available-for-sale securities, at fair value	984	986
Debt Securities \| Mortgage-backed Securities - Residential
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	488,087	425,557
Gross unrealized gains	58	374
Gross unrealized losses	(20,431)	(7,150)
Available-for-sale securities, at fair value	467,714	418,781
Debt Securities \| Municipals, Tax Exempt
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	132,450	107,127
Gross unrealized gains	950	2,692
Gross unrealized losses	(2,728)	(568)
Available-for-sale securities, at fair value	130,672	109,251
Debt Securities \| Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	7,374	7,345
Gross unrealized losses	(243)	(93)
Available-for-sale securities, at fair value	$ 7,131	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.

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- Definition

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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&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

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+ References

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