Income Taxes - Reconciliation Of Actual To Expected Tax Expense (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 “expected” income tax expense									$ 8,330	$ 7,365	$ 9,491
State income taxes, net									1,225	384	794
Tax-exempt interest on investment securities									(597)	(566)	(507)
Amortization of investment in low income housing tax credit partnerships									2,276	2,868	2,684
Low income housing credits									(3,468)	(3,540)	(2,446)
Revaluation of deferred tax assets									2,678	0	0
Other									(123)	(459)	(1,232)
Total	$ 4,085	$ 2,980	$ 1,455	$ 1,801	$ 1,458	$ 1,027	$ 1,868	$ 1,699	$ 10,321	$ 6,052	$ 8,784