Note 9. Troubled Debt Restructuring (Detail) - Type of Modifications on Troubled Debt Restructurings (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Commercial Real Estate Other Receivable [Member] Reduction of Interest Rate [Member]	Jun. 30, 2012 Commercial Real Estate Other Receivable [Member] Interest-Only Payments [Member]	Jun. 30, 2012 Commercial Real Estate Other Receivable [Member]	Jun. 30, 2012 Residential Real Estate Loans [Member] Modification of Terms [Member]	Jun. 30, 2011 Residential Real Estate Loans [Member] Modification of Terms [Member]	Jun. 30, 2012 Residential Real Estate Loans [Member] Reduction of Interest Rate [Member]	Jun. 30, 2011 Residential Real Estate Loans [Member] Reduction of Interest Rate [Member]	Jun. 30, 2012 Residential Real Estate Loans [Member] Interest-Only Payments [Member]	Jun. 30, 2011 Residential Real Estate Loans [Member] Interest-Only Payments [Member]	Jun. 30, 2012 Residential Real Estate Loans [Member]	Jun. 30, 2011 Residential Real Estate Loans [Member]	Jun. 30, 2011 Installment and Other Loans [Member] Modification of Terms [Member]	Jun. 30, 2012 Installment and Other Loans [Member] Reduction of Interest Rate [Member]	Jun. 30, 2011 Installment and Other Loans [Member] Reduction of Interest Rate [Member]	Jun. 30, 2012 Installment and Other Loans [Member]	Jun. 30, 2011 Installment and Other Loans [Member]	Jun. 30, 2012 Modification of Terms [Member]	Jun. 30, 2011 Modification of Terms [Member]	Jun. 30, 2012 Reduction of Interest Rate [Member]	Jun. 30, 2011 Reduction of Interest Rate [Member]	Jun. 30, 2012 Interest-Only Payments [Member]	Jun. 30, 2011 Interest-Only Payments [Member]	Jun. 30, 2012	Jun. 30, 2011
Count	139	114	4	6	10	3	1	16	21	1	4	20	26	2	2	3	2	5	3	3	22	24	7	4	32	31
Balance (in Dollars)			$ 2,387,610.0	$ 2,279,191.0	$ 4,666,801.0	$ 206,980.0	$ 60,827.0	$ 1,539,525.0	$ 2,760,872.0	$ 14,023.0	$ 2,354,170.0	$ 1,760,528.0	$ 5,175,869.0	$ 31,526.0	$ 82,374.0	$ 19,116.0	$ 82,374.0	$ 50,642.0	$ 206,980.0	$ 92,353.0	$ 4,009,509.0	$ 2,779,988.0	$ 2,293,214.0	$ 2,354,170.0	$ 6,509,703.0	$ 5,226,511.0