Allowance for Credit Losses (Rollforward of Allowance for Credit Losses) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011	Sep. 30, 2012		Sep. 30, 2011	Dec. 31, 2011
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance							$ 14,344
Ending Balance	14,058			14,058			14,344
Total recorded investment	3,628,251	[1]		3,628,251	[1]		3,936,369	[1]
Banking on Business Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	2,773		2,998	3,223		5,753
Charge-offs	(94)		(353)	(673)		(916)
Provision (benefit) for credit losses	(175)		60	(46)		(2,132)
Ending Balance	2,504		2,705	2,504		2,705
Ending balance, individually evaluated for impairment	94		87	94		87
Ending balance, collectively evaluated for impairment	2,410		2,618	2,410		2,618
Individually evaluated for impairment, with or without a related allowance	264		305	264		305
Collectively evaluated for impairment	15,550		17,143	15,550		17,143
Total recorded investment	15,814	[1]	17,448	15,814	[1]	17,448	17,389	[1]
Residential Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	14,066		9,150	14,344		3,150
Charge-offs	(27)		(41)	(382)		(202)
Provision (benefit) for credit losses	19		2,418	96		8,579
Ending Balance	14,058		11,527	14,058		11,527
Ending balance, individually evaluated for impairment	253		102	253		102
Ending balance, collectively evaluated for impairment	13,805		11,425	13,805		11,425
Individually evaluated for impairment, with or without a related allowance	5,956		2,859	5,956		2,859
Collectively evaluated for impairment	3,238,985		3,706,369	3,238,985		3,706,369
Total recorded investment	$ 3,244,941		$ 3,709,228	$ 3,244,941		$ 3,709,228

[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.