Variable Interest Entities (Details) (USD $)	Sep. 30, 2011 Entity Plan Contract State	Dec. 31, 2010	Sep. 30, 2010
Variable Interest Entities
Affordable housing investments	$ 109,863,000	$ 99,670,000	$ 98,667,000
Unfunded commitments for affordable housing investments	28,200,000
Number of significant variable interest in affordable housing partnerships (in entities)	4
Maximum exposure to loss	3,200,000
Aggregate carrying value of variable interest entities	$ 40,100,000	$ 37,500,000	$ 36,700,000