Derivative Instruments (Details) (Interest rate swap [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended				3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Accrued Interest Payable and Other Liabilities [Member]	Dec. 31, 2012 Accrued Interest Payable and Other Liabilities [Member]	Mar. 31, 2013 Interest Expense Subordinated Debentures [Member]	Mar. 31, 2012 Interest Expense Subordinated Debentures [Member]	Mar. 31, 2013 Other Income [Member]	Mar. 31, 2012 Other Income [Member]
Amounts and locations of activity related to the interest rate swaps designated as cash flow hedges within the Corporation's consolidated balance sheet and statement of income
Interest expense, Fair Value					$ (97)	$ (95)
Interest rate contracts	75	63
Interest rate contracts			(1,630)	(1,745)
Other income							$ 0	$ 0