Securitized Mortgage Trusts - Securitized Mortgage Trust Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Securitized Mortgage Trust Liabilities [Abstract]
Securitized mortgage borrowings	$ 3,296,242	$ 3,653,265

This element represents carrying value as of the balance sheet date securitized mortgage borrowings which consist of individual tranches of bonds issued by securitization trusts and are primarily backed by mortgage loans.

No definition available.

Name:	imh_SecuritizedMortgageBorrowings
Namespace Prefix:	imh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant