Acquisitions - Summary of Merger-Related Expenses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Summary of merger-related expenses
Salaries and employee benefits	$ 339,332	$ 321,746	$ 1,019,019	$ 991,530
Equipment and net occupancy	66,220	64,248	195,657	194,667
Printing, postage and supplies	9,752	8,272	30,749	31,512
Other costs of operations	217,817	183,875	558,905	540,927
Bank Acquisition [Member]
Summary of merger-related expenses
Salaries and employee benefits			836	4,997
Equipment and net occupancy			690	15
Printing, postage and supplies			1,825
Other costs of operations			9,013	4,867
Total merger-related expenses			$ 12,364	$ 9,879