Fair Value of Financial Instruments - Additional Information (Details)	3 Months Ended
Mar. 31, 2021 dealer
Fair Value Disclosures [Abstract]
Number of dealers received quotes from, trading	3

Trading Securities, Quotes Received, Number of Dealers

No definition available.

Name:	arr_TradingSecuritiesQuotesReceivedNumberofDealers
Namespace Prefix:	arr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration