Securities Available-for-Sale - Composition of Securities Available-for-Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 704,624	$ 686,205
Gross Unrealized Gains	11,824	10,754
Gross Unrealized Losses	(3,250)	(3,472)
Fair Value	713,198	693,487
US Treasury Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	24,904	24,891
Gross Unrealized Gains	24	47
Gross Unrealized Losses	(91)	(127)
Fair Value	24,837	24,811
Obligations of U.S. Government Corporations and Agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	220,721	230,989
Gross Unrealized Gains	1,408	1,573
Gross Unrealized Losses	(421)	(383)
Fair Value	221,708	232,179
Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	125,466	130,046
Gross Unrealized Gains	462	465
Gross Unrealized Losses	(773)	(734)
Fair Value	125,155	129,777
Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	35,132	36,606
Gross Unrealized Gains	928	984
Gross Unrealized Losses	(236)	(232)
Fair Value	35,824	37,358
Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	163,396	127,311
Gross Unrealized Gains	308	243
Gross Unrealized Losses	(1,727)	(1,950)
Fair Value	161,977	125,604
Obligations of States and Political Subdivisions
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	127,638	128,783
Gross Unrealized Gains	4,659	3,772
Gross Unrealized Losses	0	(46)
Fair Value	132,297	132,509
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	697,257	678,626
Gross Unrealized Gains	7,789	7,084
Gross Unrealized Losses	(3,248)	(3,472)
Fair Value	701,798	682,238
Marketable Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,367	7,579
Gross Unrealized Gains	4,035	3,670
Gross Unrealized Losses	(2)	0
Fair Value	$ 11,400	$ 11,249

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=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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
-Name Accounting Standards Codification
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-Section S99
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