Acquisitions - Additional Information (Detail) (USD $)				3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Aug. 27, 2012	Mar. 31, 2014 Hudson City [Member]	Mar. 31, 2013 Hudson City [Member]	Aug. 27, 2012 Common stock [Member]	Aug. 27, 2012 Cash [Member]
Business Acquisition [Line Items]
Purchase consideration per common share			$ 0.08403
Percentage of total consideration						60.00%	40.00%
Total consideration to be paid	$ 5,200,000,000
Assets	88,530,360,000	85,162,391,000		38,200,000,000
Loans				23,800,000,000
Investment securities	10,364,249,000	8,796,497,000		8,500,000,000
Liabilities	76,643,497,000	73,856,859,000		33,400,000,000
Deposits	68,699,366,000	67,118,612,000		21,100,000,000
Merger-related expenses				$ 0	$ 4,732,000