Loans (Balances Of Commercial Loan Portfolio Classes, Disaggregated By PD Grade) (Details) (USD $)	Mar. 31, 2012	Mar. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	100.00%	100.00%
Total loans collectively evaluated for impairment	$ 15,483,464,000	$ 15,353,030,000
Total loans individually evaluated for impairment	487,866,000	619,342,000
Total commercial loans	9,052,000,000	8,427,000,000
General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial loans	6,221,000,000	5,994,000,000
Loans To Mortgage Companies [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial loans	1,071,000,000	384,000,000
TRUPs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial loans	413,000,000	430,000,000	[1]
LOCOM valuation allowance	34,200,000	35,600,000
Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial loans	1,247,000,000	1,398,000,000
Residential CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial loans	100,000,000	221,000,000
Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total commercial loans	166,000,000	344,000,000
PD Grade 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	185,000,000	89,000,000
Percent of Total	2.00%	1.00%
PD Grade 1 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	185,000,000	89,000,000
PD Grade 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	192,000,000	100,000,000
Percent of Total	2.00%	1.00%
PD Grade 2 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	189,000,000	97,000,000
PD Grade 2 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	3,000,000	3,000,000
PD Grade 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	184,000,000	166,000,000
Percent of Total	2.00%	2.00%
PD Grade 3 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	163,000,000	151,000,000
PD Grade 3 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	21,000,000	15,000,000
PD Grade 4 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	222,000,000	201,000,000
Percent of Total	2.00%	2.00%
PD Grade 4 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	216,000,000	194,000,000
PD Grade 4 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	6,000,000	7,000,000
PD Grade 4 [Member] | Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade		1,000,000
PD Grade 5 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	415,000,000	326,000,000
Percent of Total	5.00%	4.00%
PD Grade 5 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	384,000,000	300,000,000
PD Grade 5 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	31,000,000	26,000,000
PD Grade 5 [Member] | Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	1,000,000	1,000,000
PD Grade 6 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	1,107,000,000	785,000,000
Percent of Total	12.00%	9.00%
PD Grade 6 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	883,000,000	686,000,000
PD Grade 6 [Member] | Loans To Mortgage Companies [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	123,000,000	44,000,000
PD Grade 6 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	97,000,000	54,000,000
PD Grade 6 [Member] | Residential CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	4,000,000	1,000,000
PD Grade 6 [Member] | Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	4,000,000	7,000,000
PD Grade 7 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	1,540,000,000	1,059,000,000
Percent of Total	17.00%	13.00%
PD Grade 7 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	886,000,000	841,000,000
PD Grade 7 [Member] | Loans To Mortgage Companies [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	434,000,000	108,000,000
PD Grade 7 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	214,000,000	107,000,000
PD Grade 7 [Member] | Residential CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	6,000,000	3,000,000
PD Grade 7 [Member] | Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	9,000,000	10,000,000
PD Grade 8 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	1,497,000,000	1,408,000,000
Percent of Total	16.00%	17.00%
PD Grade 8 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	979,000,000	1,073,000,000
PD Grade 8 [Member] | Loans To Mortgage Companies [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	367,000,000	157,000,000
PD Grade 8 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	151,000,000	174,000,000
PD Grade 8 [Member] | Residential CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade		4,000,000
PD Grade 8 [Member] | Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	13,000,000	18,000,000
PD Grade 9 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	898,000,000	751,000,000
Percent of Total	10.00%	9.00%
PD Grade 9 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	609,000,000	539,000,000
PD Grade 9 [Member] | Loans To Mortgage Companies [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	128,000,000	74,000,000
PD Grade 9 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	158,000,000	132,000,000
PD Grade 9 [Member] | Residential CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	3,000,000	6,000,000
PD Grade 9 [Member] | Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	12,000,000	19,000,000
PD Grade 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	606,000,000	522,000,000
Percent of Total	7.00%	6.00%
PD Grade 10 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	491,000,000	411,000,000
PD Grade 10 [Member] | Loans To Mortgage Companies [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	19,000,000
PD Grade 10 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	94,000,000	108,000,000
PD Grade 10 [Member] | Residential CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	2,000,000	3,000,000
PD Grade 10 [Member] | Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	9,000,000	12,000,000
PD Grade 11 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	590,000,000	606,000,000
Percent of Total	7.00%	7.00%
PD Grade 11 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	464,000,000	476,000,000
PD Grade 11 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	125,000,000	129,000,000
PD Grade 11 [Member] | Residential CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	1,000,000	1,000,000
PD Grade 11 [Member] | Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	12,000,000	21,000,000
PD Grade 12 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	172,000,000	247,000,000
Percent of Total	2.00%	3.00%
PD Grade 12 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	153,000,000	213,000,000
PD Grade 12 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	16,000,000	27,000,000
PD Grade 12 [Member] | Residential CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	3,000,000	7,000,000
PD Grade 12 [Member] | Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	4,000,000	9,000,000
PD Grade 13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	635,000,000	798,000,000
Percent of Total	7.00%	10.00%
PD Grade 13 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	226,000,000	358,000,000
PD Grade 13 [Member] | TRUPs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	334,000,000	288,000,000	[1]
PD Grade 13 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	67,000,000	143,000,000
PD Grade 13 [Member] | Residential CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	8,000,000	9,000,000
PD Grade 13 [Member] | Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	12,000,000	44,000,000
PD Grade 14,15,16 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	542,000,000	933,000,000
Percent of Total	6.00%	11.00%
PD Grade 14,15,16 [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	311,000,000	414,000,000
PD Grade 14,15,16 [Member] | Loans To Mortgage Companies [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade		1,000,000
PD Grade 14,15,16 [Member] | TRUPs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	4,000,000	80,000,000	[1]
PD Grade 14,15,16 [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	198,000,000	338,000,000
PD Grade 14,15,16 [Member] | Residential CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	29,000,000	100,000,000
PD Grade 14,15,16 [Member] | Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	53,000,000	134,000,000
Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	8,785,000,000	7,991,000,000
Total loans individually evaluated for impairment	267,000,000	436,000,000
Commercial Loan [Member] | General C&I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	6,139,000,000	5,842,000,000
Total loans individually evaluated for impairment	82,000,000	152,000,000
Commercial Loan [Member] | Loans To Mortgage Companies [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	1,071,000,000	384,000,000
Commercial Loan [Member] | TRUPs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	338,000,000	368,000,000	[1]
Total loans individually evaluated for impairment	75,000,000	62,000,000	[1]
Commercial Loan [Member] | Income CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	1,181,000,000	1,263,000,000
Total loans individually evaluated for impairment	66,000,000	135,000,000
Commercial Loan [Member] | Residential CRE [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	56,000,000	134,000,000
Total loans individually evaluated for impairment	44,000,000	87,000,000
Commercial Loan [Member] | Allowance For Loan Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	129,000,000	276,000,000
Total loans individually evaluated for impairment	$ 37,000,000	$ 68,000,000
Collectively Evaluated For Impairment [Member] | Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	97.00%	95.00%
Individually Evaluated For Impairment [Member] | Commercial Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Total	3.00%	5.00%

[1] Balances as of March 31, 2012 and 2011 presented net of $34.2 million and $35.6 million respectively lower of cost or market ("LOCOM") valuation allowance. Based on the underlying structure of the notes, the highest possible internal grade is "13". Portfolio reserve estimate considers recent financial performance of individual borrowers and other factors.