Total interest bearing deposits (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Deposit Liabilities [Line Items]
Deposits Savings Deposits	$ 6,631,518	$ 6,473,215	$ 6,274,716
Deposits Negotiable Order Of Withdrawal N O W Money Market Account And Other Demand Deposits	5,276,207	5,103,398	4,991,617
Total savings, NOW, money market and other interest bearing demand deposits	11,907,725	11,576,613	11,266,333
Time Deposits Abstract
Time Deposits Less Than 100000	6,066,658	6,473,095	6,402,998
Time Deposits 100000 Or More	3,856,933	4,236,945	4,614,334
Total certificates of deposit	9,923,591	10,710,040	11,017,332
Total interest bearing deposits	$ 21,831,316	$ 22,286,653	$ 22,283,665