Acquisitions - Summary of Merger-Related Expenses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Business Acquisition [Line Items]
Salaries and employee benefits	$ 321,746	$ 325,197	$ 991,530	$ 891,465
Equipment and net occupancy	64,248	68,101	194,667	184,434
Printing, postage and supplies	8,272	10,593	31,512	29,518
Other costs of operations	183,875	214,026	540,927	516,209
K Bank and Wilmington Trust Corporation Acquisition [Member]
Business Acquisition [Line Items]
Salaries and employee benefits		285	4,997	15,597
Equipment and net occupancy		119	15	223
Printing, postage and supplies		723		1,188
Other costs of operations		24,876	4,867	50,286
Total merger-related expenses		$ 26,003	$ 9,879	$ 67,294