Income Taxes (Reconciliation of Expected Income Tax Benefit Computed Using Federal Statutory Income Tax Rate) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Computed tax expense(1)	[1]									$ 15,032	$ 13,813	$ 21,824
Change in federal corporate income tax rate(1)	[1]									0	0	14,263
Tax exempt income										(738)	(741)	(1,291)
Income from life insurance										(509)	(510)	(829)
State taxes, net of federal benefit										1,003	905	630
Share-based awards										(60)	(250)	(390)
Low income housing credits										(430)	(465)	(366)
Other										78	(46)	37
Income tax expense		$ 3,921	$ 3,696	$ 3,275	$ 3,484	$ 3,502	$ 3,238	$ 2,887	$ 3,079	14,376	12,706	33,878
Income before income taxes		$ 19,159	$ 18,184	$ 16,479	$ 17,757	$ 17,479	$ 17,295	$ 15,104	$ 15,899	$ 71,579	$ 65,777	$ 62,354
Effective tax rate										20.10%	19.30%	54.30%

[1] (1)On December 22, 2017, the Tax Act was enacted, reducing the U.S. federal corporate income tax rate from 35.0% to 21.0%. The Company recognized the effect of the tax law changes in the period of enactment, which resulted in a reduction to net deferred tax assets and a corresponding charge to income tax expense of $14.3 million.