Reconciliation of Statutory Federal Income Tax Rate to Effective Income Tax Rate (Detail)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Reconciliation of Statutory Federal Tax Rate [Line Items]
Federal rate	35.00%	35.00%
State and local income taxes, net of federal income tax benefit	3.10%	3.50%
Credit for low-income housing investments	(1.80%)	(1.70%)
Tax-exempt income	(2.10%)	(2.90%)
Foreign operations	(4.40%)	(4.00%)
Other - net	(1.10%)	(0.60%)
Effective tax rate	28.70%	29.30%