Regulatory Matters (Regulatory Capital Requirements) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 risk based capital minimum capital percentage		4.00%
Astoria Financial Corporation
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 leverage	$ 1,508,479
Tier 1 leverage percentage	10.06%
Tier 1 leverage minimum capital requirement	$ 599,878
Tier 1 leverage minimum capital requirement percentage	4.00%
Tier 1 leverage to be well capitalized	$ 749,848
Tier 1 leverage capital to be well capitalized percentage	5.00%
Common equity tier 1	$ 1,388,269
Common equity tier 1 percentage	16.03%
Common equity tier 1 risk-based minimum capital requirement	$ 389,630
Common equity Tier 1 risk-based capital minimum capital requirement percentage	4.50%
Common equity tier 1 to be well capitalized	$ 562,798
Common equity tier 1 risk-based to be well capitalized percentage	6.50%
Tier 1 risk based capital	$ 1,508,479
Tier 1 risk based capital percentage	17.42%
Tier 1 risk based capital minimum capital requirement	$ 519,506
Tier 1 risk based capital minimum capital percentage	6.00%
Tier 1 risk based capital to be well capitalized	$ 692,675
Tier 1 risk based capital to be well capitalized percentage	8.00%
Total risk based capital	$ 1,613,140
Total risk based capital percentage	18.63%
Total risk based capital minimum capital requirement	$ 692,675
Total risk based capital minimum capital requirement percentage	8.00%
Total risk based capital to be well capitalized	$ 865,844
Total risk based capital to be well capitalized percentage	10.00%
Astoria Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 leverage	$ 1,640,848
Tier 1 leverage percentage	11.00%
Tier 1 leverage minimum capital requirement	$ 596,649
Tier 1 leverage minimum capital requirement percentage	4.00%
Tier 1 leverage to be well capitalized	$ 745,811
Tier 1 leverage capital to be well capitalized percentage	5.00%
Common equity tier 1	$ 1,640,848
Common equity tier 1 percentage	19.00%
Common equity tier 1 risk-based minimum capital requirement	$ 388,548
Common equity Tier 1 risk-based capital minimum capital requirement percentage	4.50%
Common equity tier 1 to be well capitalized	$ 561,237
Common equity tier 1 risk-based to be well capitalized percentage	6.50%
Tier 1 risk based capital	$ 1,640,848
Tier 1 risk based capital percentage	19.00%
Tier 1 risk based capital minimum capital requirement	$ 518,065
Tier 1 risk based capital minimum capital percentage	6.00%
Tier 1 risk based capital to be well capitalized	$ 690,753
Tier 1 risk based capital to be well capitalized percentage	8.00%
Total risk based capital	$ 1,745,509
Total risk based capital percentage	20.22%
Total risk based capital minimum capital requirement	$ 690,753
Total risk based capital minimum capital requirement percentage	8.00%
Total risk based capital to be well capitalized	$ 863,441
Total risk based capital to be well capitalized percentage	10.00%

Common Equity Tier 1 Risk Based Capital Required to be Well Capitalized

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Common Equity Tier 1 capital divided by risk weighted assets as defined by regulations.

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Common Equity Tier One Risk Based Capital

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The common equity Tier 1 capital ratio (common equity tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" in the regulatory framework for prompt corrective action.

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Common Equity Tier One Risk Based Capital Required for Capital Adequacy

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The minimum common equity Tier 1 Risk Based Capital ratio (common equity tier 1 capital divided by risk weighted assets) required for capital adequacy purposes in the regulatory framework for prompt corrective action.

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The amount of total capital as defined in the regulations.

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The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action.

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The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

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Total Capital divided by risk weighted assets as defined in the regulations.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital.

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The minimum amount of Tier 1 Leverage Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action.

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Tier 1 Leverage Capital divided by average assets as defined in the regulations.

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Tier 1 Risk Based Capital as defined in the regulations.

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The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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Tier 1 capital divided by risk weighted assets as defined by regulations.

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