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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Computed tax expense										$ 21,824	$ 20,139	$ 10,801
Change in federal corporate income tax rate										14,263	0	0
Tax exempt income										(1,291)	(1,312)	(1,092)
Income from life insurance										(829)	(908)	(588)
State taxes, net of federal benefit										630	565	373
Share-based awards(1)	[1]									(390)	(701)	0
Low income housing credits										(366)	(376)	(359)
Non-deductible acquisition-related costs										0	0	467
Other										37	65	305
Income tax expense		$ 19,335	$ 5,478	$ 4,721	$ 4,344	$ 4,730	$ 5,042	$ 4,258	$ 3,442	33,878	17,472	9,907
Income before income taxes		$ 16,162	$ 16,817	$ 14,955	$ 14,420	$ 15,632	$ 15,945	$ 13,874	$ 12,088	$ 62,354	$ 57,539	$ 30,859
Effective tax rate										54.30%	30.40%	32.10%

[1] (1) The Company adopted the provisions of ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, in calendar year 2016. Prior to adoption, it accounted for its windfall tax benefits or shortfalls generated upon exercise of a non-qualified stock option or a disqualifying incentive stock option, or upon vesting of its restricted shares through shareholders' equity (or as income tax expense to the extent the Company did not have a windfall tax benefit surplus). Upon adoption, the Company now accounts for its windfall tax benefits and shortfalls generated within income tax expense on the consolidated statements of income as a discrete period item in the quarter generated.