The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
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- Definition

The expense recognized in the current period that allocates the cost of nonproduction tangible assets over their useful lives.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of acquisition of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

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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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No definition available.

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Office Properties and Equipment, net - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2016
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 863
Depreciation and amortization of office properties and equipment	$ 863	$ 3,839		$ 3,364	$ 3,178
Land and building improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, additions		$ 8,900	$ 5,500