Acquisitions (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Summary of merger-related expenses
Salaries and employee benefits	$ 346,098	$ 266,090
Equipment and net occupancy	65,043	56,663
Printing, postage and supplies	11,872	9,202
Other costs of operations	170,959	136,208
K Bank and Wilmington Trust Corporation Acquisition [Member]
Summary of merger-related expenses
Salaries and employee benefits	1,973	7
Equipment and net occupancy	15	79
Printing, postage and supplies		147
Other costs of operations	740	4,062
Total merger-related expenses	$ 2,728	$ 4,295