Deposits (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Certificates of deposit
2015, weighted average rate (as a percent)	1.44%
2016, weighted average rate (as a percent)	1.78%
2017, weighted average rate (as a percent)	1.09%
2018, weighted average rate (as a percent)	1.10%
2019, weighted average rate (as a percent)	1.50%
2020 and thereafter, weighted average rate (as a percent)	1.70%
Total, weighted average rate (as a percent)	1.47%
2015, balance	$ 1,577,360us-gaap_TimeDepositMaturitiesYearOne
2016, balance	551,619us-gaap_TimeDepositMaturitiesYearTwo
2017, balance	277,620us-gaap_TimeDepositMaturitiesYearThree
2018, balance	101,213us-gaap_TimeDepositMaturitiesYearFour
2019, Balance	186,384us-gaap_TimeDepositMaturitiesYearFive
2020 and thereafter, balance	1,310
Total, balance	$ 2,695,506us-gaap_TimeDeposits	$ 3,291,797us-gaap_TimeDeposits
2015 (as a percent)	58.52%
2016 (as a percent)	20.46%
2017 (as a percent)	10.30%
2018 (as a percent)	3.76%
2019 (as a percent)	6.91%
2020 and thereafter (as a percent)	0.05%
Percent of total	100.00%af_PercentageOfTimeDepositLiabilities

Percentage of total time deposit liabilities.

No definition available.

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Percentage of time deposits with a remaining term of greater than five years to total time deposit liabilities.

+ References

No definition available.

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- Definition

Percentage of time deposits with a remaining term of greater than four years but five years or less to total time deposit liabilities.

+ References

No definition available.

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- Definition

Percentage of time deposits with a remaining term of greater than three years but four years or less to total time deposit liabilities.

+ References

No definition available.

+ Details

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- Definition

Percentage of time deposits with a remaining term of twelve months or less to total time deposit liabilities.

+ References

No definition available.

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- Definition

Percentage of time deposits with a remaining term of greater than two years, but three years or less to total time deposit liabilities.

+ References

No definition available.

+ Details

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- Definition

Percentage of time deposits with a remaining term of greater than twelve months, but two years or less to total time deposit liabilities.

+ References

No definition available.

+ Details

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- Definition

Amount of time deposits maturing after the fifth fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

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Amount of time deposits maturing in the fifth fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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Amount of time deposits maturing in the fourth fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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Amount of time deposits maturing in the next fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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- Definition

Amount of time deposits maturing in the third fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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- Definition

Amount of time deposits maturing in the second fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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Amount of deposits that cannot be withdrawn before a set date without penalty or for which notice of withdrawal is required. Time deposits include, but are not limited to, certificates of deposits, individual retirement accounts and open accounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 12

-Article 9

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- Definition

Weighted average interest rate for time deposits held by the entity with maturities greater than five years.

+ References

No definition available.

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Weighted average interest rate for time deposits held by the entity with maturities greater than four years, but five years or less.

+ References

No definition available.

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Weighted average interest rate for time deposits held by the entity with maturities greater than three years, but four years or less.

+ References

No definition available.

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- Definition

Weighted average interest rate for time deposits held by the entity with maturities of one year or less.

+ References

No definition available.

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Weighted average interest rate for time deposits held by the entity with maturities greater than two years, but three years or less.

+ References

No definition available.

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Weighted average interest rate for time deposits held by the entity with maturities greater than one year, but two years or less.

+ References

No definition available.

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The weighted average interest rate for domestic time deposit liabilities.

+ References

No definition available.

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