Guarantees (Details) (USD $)	Mar. 31, 2012
Financial Standby Letter Of Credit [Member]
Guarantor Obligations [Line Items]
Guarantor obligations, Net liability	$ 5,200,000
Guaranteed maximum potential future payments	366,300,000
Indirect Guarantee Of Indebtedness [Member]
Guarantor Obligations [Line Items]
Guarantor obligations, Net liability	115,000
Notional amount of underlying interest rate swaps associated with risk participation agreements	37,300,000
Payment required if event of default on all contracts occurred	$ 3,500,000
RPA's, minimum in years	5
RPA's, maximum in years	10