Variable Interest Entities (Details) (USD $)	Dec. 31, 2011 entity	Dec. 31, 2010
Variable Interest Entities
Affordable housing investments	$ 121,039,000	$ 99,670,000
Unfunded commitments for affordable housing investments	39,600,000
Number of significant variable interest in affordable housing partnerships (in entities)	4
Maximum exposure to loss	2,200,000
Aggregate carrying value of private equity and alternative investment funds that are variable interest entities	$ 39,900,000	$ 37,500,000