Other assets by major categories (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]
Net deferred tax assets (net of valuation allowance)	$ 572,744	$ 429,691
Investments under the equity method	223,960	313,152
Bank Owned Life Insurance	231,428	238,077
Prepaid F D I C Insurance Assessment	32,617	58,082
Prepaid Taxes	107,827	17,441
Other prepaid expenses	56,063	59,894
Derivative Fair Value Of Derivative Asset	53,244	61,886
Trades receivables from brokers and counterparties	87,774	69,535	37,196
Others	212,137	214,635
Total other assets	$ 1,577,794	$ 1,462,393