Other assets by major categories (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]
Net deferred tax assets (net of valuation allowance)	$ 545,859	$ 429,691
Investments under the equity method	218,045	313,152
Bank Owned Life Insurance	232,499	238,077
Prepaid F D I C Insurance Assessment	30,053	58,082
Prepaid Taxes	99,500	17,441
Other prepaid expenses	60,841	59,894
Derivative Fair Value Of Derivative Asset	49,879	61,886
Trades receivables from brokers and counterparties	287,322	69,535	855,567
Others	200,929	214,635
Total other assets	$ 1,724,927	$ 1,462,393