Income Tax Expense (Schedule of Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Tax expense at Federal statutory rate	$ 22,520	$ 20,938	$ 18,438
(Decrease) increase in taxes resulting from:
Tax-exempt income	(1,604)	(1,540)	(1,408)
Dividends received deduction	(57)	(29)	0
BOLI	(694)	(646)	(648)
Federal tax credits	(364)	(364)	(364)
Acquisition related expenses	318	0	0
State income tax expense, net of federal income tax benefit	658	581	461
Other	101	59	48
Total income tax expense	$ 20,878	$ 18,999	$ 16,527