Cash and Cash Equivalents (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011	Dec. 31, 2010
Cash, Cash Equivalents Details [Line Items]
Cash and due from banks	$ 598,916	[1]	$ 852,010	[1]
Securities purchased under agreements to resell	161,594	[2]	175,553	[2]
Other short-term investment securities	90,114		87,385
Total cash and cash equivalents	$ 850,624		$ 1,114,948		$ 2,350,060	$ 3,076,432

[1] At March 31, 2012 and December 31, 2011, $76.9 million and $100.1 million, respectively, of our cash and due from banks was deposited at the FRB and was earning interest at the Federal Funds target rate, and interest-earning deposits in other financial institutions were $267.2 million and $371.5 million, respectively.

[2] At March 31, 2012 and December 31, 2011, securities purchased under agreements to resell were collateralized by U.S. treasury securities and U.S. agency securities with aggregate fair values of $164.8 million and $179.1 million, respectively. None of these securities received as collateral were sold or repledged as of March 31, 2012 and December 31, 2011.