Allowance for Credit Losses (Credit Quality Indicators) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Dec. 31, 2011		Sep. 30, 2012 Conventional Loan [Member]		Dec. 31, 2011 Conventional Loan [Member]		Sep. 30, 2012 Government-Insured Mortgage Loans [Member]		Dec. 31, 2011 Government-Insured Mortgage Loans [Member]		Sep. 30, 2012 Banking on Business Loans [Member]		Dec. 31, 2011 Banking on Business Loans [Member]		Sep. 30, 2011 Banking on Business Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Past due 30-59 days	$ 65,715	[1]	$ 86,407	[1]	$ 48,970	[1]	$ 60,998	[1]	$ 16,745	[1]	$ 25,077	[1]	$ 0	[1]	$ 332	[1]
Past due 60-89 days	15,937	[1]	26,140	[1]	11,169	[1]	16,810	[1]	4,623	[1]	9,290	[1]	145	[1]	40	[1]
Past Due 90 to 179 days	20,154	[1]	28,869	[1]	15,948	[1]	22,749	[1]	4,104	[1]	5,740	[1]	102	[1]	380	[1]
Past Due Equal to or Greater than 180 days	59,153	[1]	64,130	[1]	56,571	[1]	60,887	[1]	2,467	[1]	2,947	[1]	115	[1]	296	[1]
Total past due loans	160,959	[1]	205,546	[1]	132,658	[1]	161,444	[1]	27,939	[1]	43,054	[1]	362	[1]	1,048	[1]
Total current loans	3,467,292	[1]	3,730,823	[1]	3,112,283	[1]	3,402,834	[1]	339,557	[1]	311,648	[1]	15,452	[1]	16,341	[1]
Total recorded investment	3,628,251	[1]	3,936,369	[1]	3,244,941	[1]	3,564,278	[1]	367,496	[1]	354,702	[1]	15,814	[1]	17,389	[1]	17,448
In process of foreclosures, included above	59,927	[2]	62,548	[2]	58,797	[2]	60,533	[2]	1,130	[2]	2,015	[2]	0	[2]	0	[2]
Serious delinquency rate	2.20%		2.40%	[3]	2.20%	[3]	2.40%	[3]	1.80%	[3]	2.50%	[3]	1.40%	[3]	2.20%	[3]
Past due 90 days or more still accruing interest	6,571		8,687		0		0		6,571		8,687		0		0
Loans on nonaccrual status	$ 78,904	[4]	$ 88,636	[4]	$ 78,278	[4]	$ 87,488	[4]	$ 0	[4]	$ 0	[4]	$ 626	[4]	$ 1,148	[4]
Period Loan Receivable Becomes Nonaccrual Status	90 days

[1] The recorded investment in a loan is the unpaid principal balance of the loan, adjusted for accrued interest, net deferred loan fees or costs, unamortized premiums or discounts, adjustments for fair value hedges and direct write-downs. The recorded investment is not net of any valuation allowance.

[2] Includes loans where the decision of foreclosure or similar alternative such as pursuit of deed-in-lieu has been reported. Loans in process of foreclosure are included in past due or current loans dependent on their delinquency status.

[3] Loans that are 90 days or more past due or in the process of foreclosure expressed as a percentage of the total loan portfolio class.

[4] Generally represents mortgage loans with contractual principal or interest payments 90 days or more past due and not accruing interest.