Derivatives and Hedging Activities - Derivatives accounted for as hedges under ASC 815 (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Other assets
Derivatives accounted for as hedges under ASC 815
Derivatives accounted for as hedges, Interest Rate Products, Balance Sheet Location	Other assets	Other assets	Other assets
Derivatives accounted for as hedges, Asset derivatives. Fair Value	$ 21		$ 23
Derivatives not accounted for as hedges under ASC 815
Derivatives not accounted for as hedges, Interest Rate Products, Balance Sheet Location	Other assets	Other assets	Other assets
Derivatives not accounted for as hedges, Asset derivatives, Fair Value	581	73	635
Other liabilities
Derivatives accounted for as hedges under ASC 815
Derivatives accounted for as hedges, Interest Rate Products, Balance Sheet Location	Other liabilities	Other liabilities	Other liabilities
Derivatives accounted for as hedges, Liability derivatives, Fair Value	13,964	2,526	11,900
Derivatives not accounted for as hedges under ASC 815
Derivatives not accounted for as hedges, Interest Rate Products, Balance Sheet Location	Other liabilities	Other liabilities	Other liabilities
Derivatives not accounted for as hedges, Liability derivatives, Fair Value	$ 592	$ 73	$ 643