Regulatory Matters - Regulatory Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Jan. 01, 2015	Dec. 31, 2014
Amount
Tier 1 leverage	$ 1,521,367
Common equity tier 1 risk-based	1,401,376
Tier 1 risk-based	1,521,367
Total risk-based	$ 1,620,612
Ratio
Tier 1 leverage	10.21%
Common equity tier 1 risk-based	16.00%
Tier 1 risk-based	17.37%
Total risk-based	18.51%
Amount
Tier 1 leverage	$ 596,022
Common equity tier 1 risk-based	394,092
Tier 1 risk-based	525,456
Total risk-based	$ 700,608
Ratio
Tier 1 leverage	4.00%	4.00%
Common equity tier 1 risk-based	4.50%	4.50%
Tier 1 risk-based	6.00%	6.00%
Total risk-based	8.00%	8.00%
Amount
Tier 1 leverage	$ 745,027
Common equity tier 1 risk-based	569,244
Tier 1 risk-based	700,608
Total risk-based	$ 875,760
Ratio
Tier 1 leverage	5.00%	5.00%
Common equity tier 1 risk-based	6.50%	6.50%
Tier 1 risk-based	8.00%	8.00%
Total risk-based	10.00%	10.00%
Astoria Bank
Amount
Tier 1 leverage	$ 1,670,312		$ 1,632,390
Common equity tier 1 risk-based	1,670,312
Tier 1 risk-based	1,670,312		1,632,390
Total risk-based	$ 1,769,557		1,744,905
Tangible			$ 1,632,390
Ratio
Tier 1 leverage	11.29%		10.62%
Common equity tier 1 risk-based	19.12%
Tier 1 risk-based	19.12%		17.55%
Total risk-based	20.25%		18.76%
Tangible			10.62%
Amount
Tier 1 leverage	$ 591,787		$ 615,022
Common equity tier 1 risk-based	393,153
Tier 1 risk-based	524,204		372,118
Total risk-based	$ 698,939		744,236
Tangible			$ 230,633
Ratio
Tier 1 leverage	4.00%		4.00%
Common equity tier 1 risk-based	4.50%
Tier 1 risk-based	6.00%		4.00%
Total risk-based	8.00%		8.00%
Tangible			1.50%
Amount
Tier 1 leverage	$ 739,734		$ 768,777
Common equity tier 1 risk-based	567,888
Tier 1 risk-based	698,939		558,177
Total risk-based	$ 873,674		$ 930,295
Ratio
Tier 1 leverage	5.00%		5.00%
Common equity tier 1 risk-based	6.50%
Tier 1 risk-based	8.00%		6.00%
Total risk-based	10.00%		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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Compliance with Regulatory Capital Requirements under Banking Regulations, Actual Capital, Amount [Abstract]

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Compliance with Regulatory Capital Requirements under Banking Regulations, Actual Capital, Ratio [Abstract]

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Compliance with Regulatory Capital Requirements under Banking Regulations, Minimum Capital Requirement, Amount [Abstract]

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Compliance with Regulatory Capital Requirements under Banking Regulations, Minimum Capital Requirement, Ratio [Abstract]

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

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

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

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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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Tangible capital as defined in the regulations (generally includes outstanding stock plus retained earnings) for banking institutions subject to Office of Thrift Supervision (OTS) capital requirements.

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The minimum amount of tangible capital required under the regulatory framework for prompt corrective action.

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The minimum amount of Tangible Capital divided by tangible assets (Tangible Capital Ratio) as defined in the regulations.

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Tangible Capital divided by Tangible assets as defined in the regulations.

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

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The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" 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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