Short-term Borrowings (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Short-term Debt [Abstract]
Average daily amounts outstanding	$ 28,608	$ 26,867	$ 27,472	$ 25,122
Weighted average interest rates	1.32%	1.52%	1.35%	1.41%