Acquisitions - Summary of Merger-Related Expenses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Summary of merger-related expenses
Salaries and employee benefits	$ 348,776	$ 339,332	$ 1,059,815	$ 1,019,019
Equipment and net occupancy	67,713	66,220	206,964	195,657
Printing, postage and supplies	9,184	9,752	29,320	30,749
Other costs of operations	233,060	217,817	696,160	558,905
Hudson City [Member]
Summary of merger-related expenses
Salaries and employee benefits				836
Equipment and net occupancy				690
Printing, postage and supplies				1,825
Other costs of operations				9,013
Total merger-related expenses	$ 0	$ 0	$ 0	$ 12,364