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Securities - Fair Values and Amortized Costs Securities (Details) - USD ($)
$ in Thousands

6 Months Ended

Jun. 30, 2018

Jun. 30, 2017

Dec. 31, 2017

Debt Securities, Available-for-sale [Line Items]

Debt Securities, Available-for-Sale, Amortized Cost

$ 693,008

Debt Securities, Available-for-Sale, Gross Unrealized Gains

2,858

$ 5,645

Debt Securities, Available-for-Sale, Gross Unrealized Losses

(12,950)

(3,967)

Debt Securities, Available-for-Sale, Fair Value

682,916

693,147

Equity Securities, Fair Value

5,425

5,144

Total Securities, Amortized Cost

695,284

Total Securities, Gross Unrealized Gains

6,975

Total Securities, Gross Unrealized Losses

(3,968)

Total Securities, Fair Value

688,341

698,291

U.S. Treasury securities

Debt Securities, Available-for-sale [Line Items]

Debt Securities, Available-for-Sale, Amortized Cost

9,953

19,943

Debt Securities, Available-for-Sale, Gross Unrealized Gains

0

0

Debt Securities, Available-for-Sale, Gross Unrealized Losses

(334)

(154)

Debt Securities, Available-for-Sale, Fair Value

9,619

19,789

Obligations of U.S. government corporations and agencies

Debt Securities, Available-for-sale [Line Items]

Debt Securities, Available-for-Sale, Amortized Cost

156,812

162,045

Debt Securities, Available-for-Sale, Gross Unrealized Gains

16

341

Debt Securities, Available-for-Sale, Gross Unrealized Losses

(1,759)

(193)

Debt Securities, Available-for-Sale, Fair Value

155,069

162,193

Collateralized mortgage obligations of U.S. government corporations and agencies

Debt Securities, Available-for-sale [Line Items]

Debt Securities, Available-for-Sale, Amortized Cost

121,631

109,916

Debt Securities, Available-for-Sale, Gross Unrealized Gains

61

93

Debt Securities, Available-for-Sale, Gross Unrealized Losses

(2,950)

(1,321)

Debt Securities, Available-for-Sale, Fair Value

118,742

108,688

Residential mortgage-backed securities of U.S. government corporations and agencies

Debt Securities, Available-for-sale [Line Items]

Debt Securities, Available-for-Sale, Amortized Cost

28,662

32,388

Debt Securities, Available-for-Sale, Gross Unrealized Gains

309

679

Debt Securities, Available-for-Sale, Gross Unrealized Losses

(529)

(213)

Debt Securities, Available-for-Sale, Fair Value

28,442

32,854

Commercial mortgage-backed securities of U.S. government corporations and agencies

Debt Securities, Available-for-sale [Line Items]

Debt Securities, Available-for-Sale, Amortized Cost

254,458

244,018

^[1]

Debt Securities, Available-for-Sale, Gross Unrealized Gains

0

247

^[1]

Debt Securities, Available-for-Sale, Gross Unrealized Losses

(7,330)

(2,044)

^[1]

Debt Securities, Available-for-Sale, Fair Value

247,128

242,221

^[1]

Securities purchased pending settlement

5,900

Obligations of states and political subdivisions

Debt Securities, Available-for-sale [Line Items]

Debt Securities, Available-for-Sale, Amortized Cost

121,492

123,159

Debt Securities, Available-for-Sale, Gross Unrealized Gains

2,472

4,285

Debt Securities, Available-for-Sale, Gross Unrealized Losses

(48)

(42)

Debt Securities, Available-for-Sale, Fair Value

123,916

127,402

Total Debt Securities Available-for-Sale

Debt Securities, Available-for-sale [Line Items]

Debt Securities, Available-for-Sale, Amortized Cost

693,008

691,469

Debt Securities, Available-for-Sale, Gross Unrealized Gains

2,858

5,645

Debt Securities, Available-for-Sale, Gross Unrealized Losses

(12,950)

(3,967)

Debt Securities, Available-for-Sale, Fair Value

682,916

693,147

Marketable equity securities

Debt Securities, Available-for-sale [Line Items]

Equity Securities, FV-NI, Cost

^[2]

0

3,815

Equity Securities, FV-NI, Unrealized Gain

^[2]

0

$ 1,330

Equity Securities, FV-NI, Unrealized Loss

^[2]

0

$ (1)

Equity Securities, Fair Value

^[2]

$ 0

$ 5,144

[1]	Includes a $5.9 million security purchase that was pending settlement as of December 31, 2017.
[2]	ASU No. 2016-01 was adopted January 1, 2018, resulting in separate classification of our marketable equity securities previously included in available-for-sale securities

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