Bank subsidiary (Details 8) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	$ 40,646	$ 41,679	$ 35,798
Provision for loan losses	15,009	20,894	32,000
Charge-offs	17,749	21,927	26,119
Valuation allowance, balance at the end of the period	37,906	40,646	41,679
Ratio of net charge-offs to average loans outstanding (as a percent)	0.49%	0.61%	0.66%
Real estate loans
Allowance for loan losses:
Charge-offs	10,733	14,276	9,526
Other loans
Allowance for loan losses:
Charge-offs	$ 7,016	$ 7,651	$ 16,593