Short-Term Borrowings and Long-Term Debt (Schedule of Debt) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Long-term debt
Long-term debt outstanding at end of period	$ 20,436	$ 55,498	$ 65,559
Weighted average rate on outstanding long-term debt	2.84%	2.38%	2.27%
Maximum outstanding long-term debt of any month end	$ 55,493	$ 65,554	$ 65,593
Average outstanding long-term debt	$ 35,684	$ 58,704	$ 60,503
Approximate average rate paid on long-term debt	2.39%	2.24%	2.41%
Short-term borrowings
Short-term borrowings outstanding at end of period	$ 35,000	$ 87,500	$ 79,000
Weighted average rate on short-term borrowings	2.51%	1.34%	0.71%
Maximum outstanding short-term borrowings at any month end	$ 74,000	$ 109,000	$ 79,000
Average outstanding short-term borrowings	$ 42,286	$ 91,797	$ 39,802
Approximate average rate paid on short-term borrowings	1.81%	1.15%	0.49%