The aggregate excess of a loan's cash flows expected to be collected over the investor's initial investment in the loan. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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The price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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Loans and leases and the allowance for credit losses (Details Textual) (USD $)	3 Months Ended	12 Months Ended	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Acquired Loans [Member]	Mar. 31, 2011 Acquired Loans [Member]	Dec. 31, 2010 Acquired Loans [Member]
Loans and Leases Receivable [Line Items]
Interest income	$ 81,387,000		$ 81,000,000	$ 41,000,000
Accretable yield balance	770,031,000	838,765,000		416,000,000	457,000,000
Loans and leases and allowance for credit losses (Details) (Textual) [Abstract]
Purchased impaired loans as a percentage of total assets	Less than 1% of companys assets	Less than 1% of companys assets
Contractual principal and interest payments	$ 605,000,000	$ 653,000,000
Loan delinquent period	90 days
Maturity period of line of credit	more than 150 days