Variable Interest Entities (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Variable Interest Entities
Affordable housing investments	$ 150,466,000	$ 154,011,000
Affordable Housing VIEs - not primary beneficiary
Variable Interest Entities
Affordable housing investments	150,500,000	154,000,000
Unfunded commitments for affordable housing investments	52,900,000
Number of significant variable interest in affordable housing partnerships (in entities)	4
Unfunded commitments for affordable housing investments with significant variable interest	0
Maximum exposure to loss	2,000,000
Aggregate carrying value of private equity and alternative investment funds	$ 35,500,000	$ 36,100,000