Acquisitions (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended			1 Months Ended
	Dec. 31, 2011	Dec. 31, 2009	May 23, 2009	May 31, 2011 Wilmington Trust Corporation [Member]	May 16, 2011 Wilmington Trust Corporation [Member]
Purchase price:
Common shares issued (4,694,486 shares)			$ 273,000		$ 405,557
Preferred stock purchased from U.S. Treasury					330,000
Total purchase price			274,000		735,557
Identifiable assets:
Cash and due from banks					178,940
Interest-bearing deposits at banks					2,606,265
Other short-term investments					57,817
Investment securities					510,390
Loans and leases					6,410,430
Core deposit and other intangibles					112,094
Other assets					969,106
Total identifiable assets					10,845,042
Liabilities:
Deposits					8,864,161
Short-term borrowings					147,752
Long-term borrowings					600,830
Other liabilities					431,812
Total liabilities					10,044,555
Net gain resulting from acquisition	$ 64,930	$ 29,000		$ 64,930