Derivative Financial Instruments (Details 4) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Offsetting of financial liabilities and derivative liabilities
Gross Amounts of Recognized Liabilities	$ 122,285	$ 117,920
Gross Amounts Offset in the Statement of Financial Position	684	1,296
Net Amounts of Liabilities Presented in the Statement of Financial Position	121,601	116,624
Gross amounts not offset in the Statement of Financial Position
Financial Instruments	110,491	100,180
Cash Collateral Pledged	9,407	15,811
Net Amount	1,703	633
Repurchase agreements
Offsetting of financial liabilities and derivative liabilities
Gross Amounts of Recognized Liabilities	110,491	100,180
Net Amounts of Liabilities Presented in the Statement of Financial Position	110,491	100,180
Gross amounts not offset in the Statement of Financial Position
Financial Instruments	110,491	100,180
Interest rate swaps
Offsetting of financial liabilities and derivative liabilities
Gross Amounts of Recognized Liabilities	11,794	17,740
Gross Amounts Offset in the Statement of Financial Position	684	1,296
Net Amounts of Liabilities Presented in the Statement of Financial Position	11,110	16,444
Gross amounts not offset in the Statement of Financial Position
Cash Collateral Pledged	9,407	15,811
Net Amount	$ 1,703	$ 633