Cash and Cash Equivalents (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011		Sep. 30, 2011	Dec. 31, 2010
Disclosure Cash And Cash Equivalents [Abstract]
Cash and due from banks	$ 678,239	[1]	$ 852,010	[1]
Securities purchased under agreements to resell	116,276	[2]	175,553	[2]
Other short-term investment securities	112,165		87,385
Total cash and cash equivalents	$ 906,680		$ 1,114,948		$ 2,041,972	$ 3,076,432

[1] At September 30, 2012 and December 31, 2011, $139.1 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 $187.6 million and $371.5 million, respectively.

[2] At September 30, 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 $118.6 million and $179.1 million, respectively. None of these securities received as collateral were sold or repledged as of September 30, 2012 and December 31, 2011.