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Commitments and contingencies - Additional Information (Detail) (USD $) | 6 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2011 | Dec. 31, 2013 Property | Dec. 31, 2012 Property
Loss Contingencies [Line Items] |  |  |
Aggregate outstanding commitments |  | $ 1,453,000 | $ 1,694,000
Number of properties |  | 23,268 | 3,644
Company contributions | 93,000 | 181,000 | 163,000
Purchase Commitment [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Number of properties |  | 536 | 462
Aggregate purchase price |  | $ 75,473,000 | $ 70,082,000

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- Definition Aggregate Purchase Price + References No definition available. + Details
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- Definition Outstanding Commitment + References No definition available. + Details
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Namespace Prefix: | amh_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition The increase in the fair value of plan assets from contributions made by the employer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920 + Details
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- Details
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- Definition The number of real estate properties owned as of the balance sheet date. + References No definition available. + Details
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