| Document and Entity Information | Dec. 31, 2020 |
| Entity Listings [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Dec. 31, 2020 |
| Entity Registrant Name | ANWORTH MORTGAGE ASSET CORPORATION |
| Entity Incorporation, State or Country Code | MD |
| Entity File Number | 001-13709 |
| Entity Tax Identification Number | 52-2059785 |
| Entity Address, Address Line One | 1299 Ocean Avenue |
| Entity Address, Address Line Two | 2nd Floor |
| Entity Address, City or Town | Santa Monica |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 90401 |
| City Area Code | 310 |
| Local Phone Number | 255-4493 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001047884 |
| Common Stock [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Common Stock, $0.01 Par Value |
| Trading Symbol | ANH |
| Security Exchange Name | NYSE |
| Series A Preferred Stock [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Series A Cumulative Preferred Stock, $0.01 Par Value |
| Trading Symbol | ANHPRA |
| Security Exchange Name | NYSE |
| Series B Preferred Stock [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Series B Cumulative Convertible Preferred Stock, $0.01 Par Value |
| Trading Symbol | ANHPRB |
| Security Exchange Name | NYSE |
| Series C Preferred Stock [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Series C Cumulative Redeemable Preferred Stock, $0.01 Par Value |
| Trading Symbol | ANHPRC |
| Security Exchange Name | NYSE |
