Loans, Allowance for Loan Losses, and Credit Quality Changes in the Allowance for Loan Losses (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Changes in the allowance for loan losses
Loans and Leases Receivable, Allowance, Beginning Balance	$ 268,315	$ 297,409	$ 378,151
Provision for loan losses	13,000us-gaap_ProvisionForLoanAndLeaseLosses	10,000us-gaap_ProvisionForLoanAndLeaseLosses	3,000us-gaap_ProvisionForLoanAndLeaseLosses
Charge offs	(44,096)	(88,061)	(117,046)
Recoveries	29,083	48,967	33,304
Net charge offs	(15,013)	(39,094)	(83,742)
Loans and Leases Receivable, Allowance, Ending Balance	266,302	268,315	297,409
Change in the allowance for unfunded commitments
Allowance For Credit Losses	291,202asb_Allowanceforcreditlosses	290,215asb_Allowanceforcreditlosses	319,209asb_Allowanceforcreditlosses
Reserve for Off-balance Sheet Activities [Member]
Change in the allowance for unfunded commitments
Balance at beginning of period	21,900	21,800	14,700
Provision for unfunded commitments	3,000	100	7,100
Balance at end of period	$ 24,900	$ 21,900	$ 21,800

No authoritative reference available.

No definition available.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount, after recoveries, of loans and leases that have been written-off.

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No definition available.

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Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

+ References

No definition available.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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Amount of expense related to credit loss from transactions other than loan and lease transactions.

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Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

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