Unpaid Principal Balance of Residential and Consumer Loans Based on Accrual Status (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Mar. 31, 2012
Financing Receivable, Impaired [Line Items]
Non-Accrual	$ 118,790		$ 224,924
Total	1,763,196		2,188,083
Residential And Consumer Loans Based On Accrual Status
Financing Receivable, Impaired [Line Items]
Accrual	923,931		1,021,354
Non-Accrual	37,748		52,936
Total	961,679		1,074,290
Residential And Consumer Loans Based On Accrual Status | Residential
Financing Receivable, Impaired [Line Items]
Accrual	514,613		519,877
Non-Accrual	33,107		44,550
Total	547,720		564,427
Residential And Consumer Loans Based On Accrual Status | Education
Financing Receivable, Impaired [Line Items]
Accrual	166,005	[1]	239,569	[1]
Non-Accrual	424	[1]	762	[1]
Total	166,429	[1]	240,331	[1]
Residential And Consumer Loans Based On Accrual Status | Other consumer
Financing Receivable, Impaired [Line Items]
Accrual	243,313		261,908
Non-Accrual	4,217		7,624
Total	$ 247,530		$ 269,532

[1] Non-accrual education loans represent the portion of these loans 90+ days past due that are not covered by a guarantee provided by government agencies that is limited to approximately 97% of the outstanding balance.