Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reconciliation of Federal Statutory to Actual Tax Expense:
Federal statutory income tax at 35%	$ 11,304	$ 9,985	$ 32,900	$ 27,481
Federal statutory income tax rate	35.00%	35.00%	35.00%	35.00%
Tax-exempt interest income	$ (2,881)	$ (2,198)	$ (8,062)	$ (6,328)
Share-based compensation	(78)	(29)	(862)	(10)
Tax-exempt earnings and gains on life insurance	(551)	(216)	(1,905)	(1,186)
Tax credits	(132)	(165)	(396)	(423)
Other	277	92	639	225
Actual Tax Expense	$ 7,939	$ 7,469	$ 22,314	$ 19,759
Effective Tax Rate	24.60%	26.20%	23.70%	25.20%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other deductions.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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