Variable Interest Entities (Details) (USD $)	Dec. 31, 2012 entity	Dec. 31, 2011
Variable Interest Entities
Affordable housing investments	$ 154,011,000	$ 121,039,000
Unfunded commitments for affordable housing investments	58,600,000
Number of significant variable interest in affordable housing partnerships (in entities)	4
Maximum exposure to loss	2,300,000
Aggregate carrying value of private equity and alternative investment funds that are variable interest entities	$ 36,100,000	$ 39,900,000