Aggregate value of common shares reserved for future issuance.

No definition available.

Name:	nymt_CommonStockValueofSharesReservedforFutureIssuanceValue
Namespace Prefix:	nymt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Minimum Number of Quarters with No Dividends that Results in Voting Rights

+ References

No definition available.

+ Details

Name:	nymt_MinimumNumberofQuarterswithNoDividendsthatResultsinVotingRights
Namespace Prefix:	nymt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Preferred Stock, Percentage of Stock Holders Required for Term Changes

+ References

No definition available.

+ Details

Name:	nymt_PreferredStockPercentageofStockHoldersRequiredforTermChanges
Namespace Prefix:	nymt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Preferred Stock, Redemption Term

+ References

No definition available.

+ Details

Name:	nymt_PreferredStockRedemptionTerm
Namespace Prefix:	nymt_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Preferred Stock, Shares Reserved For Future Issuance, Value

+ References

No definition available.

+ Details

Name:	nymt_PreferredStockSharesReservedForFutureIssuanceValue
Namespace Prefix:	nymt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Preferred Stock, Voting Rights, Number of Additional Directors Elected

+ References

No definition available.

+ Details

Name:	nymt_PreferredStockVotingRightsNumberofAdditionalDirectorsElected
Namespace Prefix:	nymt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_ClassOfStockLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Face amount or stated value per share of common stock.

+ References

+ Details

Name:	us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Monetary value of common stock allocated to investors to buy shares of a new issue of common stock before they are offered to the public. When stock is sold on a subscription basis, the issuer does not initially receive the total proceeds. In general, the issuer does not issue the shares to the investor until it receives the entire proceeds.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65888546&loc=d3e21300-112643

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockSharesSubscriptions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The percentage rate used to calculate dividend payments on preferred stock.

+ References

No definition available.

+ Details

Name:	us-gaap_PreferredStockDividendRatePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The per share liquidation preference (or restrictions) of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(d)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21484-112644

+ Details

Name:	us-gaap_PreferredStockLiquidationPreference
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

+ References

+ Details

Name:	us-gaap_PreferredStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The price per share at which the preferred stock of an entity that has priority over common stock in the distribution of dividends and in the event of liquidation of the entity is redeemed or may be called at. The redemption features of this preferred stock are solely within the control of the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21488-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21564-112644

+ Details

Name:	us-gaap_PreferredStockRedemptionPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of nonredeemable preferred stock (shares) (or preferred stock redeemable solely at the option of the issuer) allocated to investors to buy shares of a new issue of preferred stock before they are offered to the public. When stock is sold on a subscription basis, the issuer does not initially receive the total proceeds. In general, the issuer does not issue the shares to the investor until it receives the entire proceeds.

+ References

+ Details

Name:	us-gaap_PreferredStockShareSubscriptions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

+ References

+ Details

Name:	us-gaap_PreferredStockSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.

+ References

+ Details

Name:	us-gaap_PreferredStockSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

+ References

+ Details

Name:	us-gaap_PreferredStockSharesOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of subscription received from investors who have been allocated nonredeemable preferred stock or preferred stock redeemable solely at the option of the issuer.

+ References

+ Details

Name:	us-gaap_PreferredStockSharesSubscribedButUnissuedValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow from the additional capital contribution to the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfCommonStock
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of new stock issued during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=nymt_UnderwrittenPublicOfferingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=us-gaap_OverAllotmentOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=nymt_EquityDistributionAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=nymt_PreferredEquityDistributionAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_SeriesBPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_SeriesCPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_SeriesDPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=nymt_SeriesBSeriesCandSeriesDPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Stockholders' Equity - Narrative (Details) $ / shares in Units, $ in Millions				3 Months Ended		12 Months Ended	18 Months Ended
	Mar. 15, 2019 USD ($) shares	Mar. 01, 2019 $ / shares shares	Jan. 11, 2019 USD ($) $ / shares shares	Mar. 31, 2019 USD ($) quarter director $ / shares shares	Mar. 31, 2018 shares	Dec. 31, 2018 $ / shares shares	Mar. 31, 2019 USD ($) quarter director $ / shares shares	Mar. 29, 2019 USD ($)	Mar. 28, 2019 shares	Sep. 10, 2018 USD ($)	Oct. 13, 2017 $ / shares	Aug. 10, 2017 USD ($) $ / shares
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)				200,000,000		200,000,000	200,000,000
Preferred stock, par value (in dollars per share) \| $ / shares				$ 0.01		$ 0.01	$ 0.01
Preferred stock, shares issued (in shares)				12,000,000		12,000,000	12,000,000
Preferred stock, shares outstanding (in shares)				12,000,000		12,000,000	12,000,000
Common stock, par value (in dollars per share) \| $ / shares				$ 0.01		$ 0.01	$ 0.01
Underwritten Public Offering
Class of Stock [Line Items]
Shares issued (in shares)	17,250,000	15,000,000	14,490,000
Share price (in dollars per share) \| $ / shares		$ 6.0	$ 5.96
Proceeds from issuance of common stock \| $	$ 101.2		$ 83.8
Over-Allotment Option
Class of Stock [Line Items]
Shares issued (in shares)	2,250,000
Equity Distribution Agreements
Class of Stock [Line Items]
Shares issued (in shares)				0	0
Common stock, par value (in dollars per share) \| $ / shares												$ 0.01
Common stock that may be sold (up to) \| $										$ 177.1		$ 100.0
Common stock reserved for issuance \| $				$ 86.4			$ 86.4					$ 39.3
Preferred Equity Distribution Agreement
Class of Stock [Line Items]
Equity agreement for preferred stock maximum aggregate sales price (up to) \| $								$ 50.0
Preferred stock available for future issuance, value \| $								$ 50.0
Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)				6,000,000		6,000,000	6,000,000
Preferred stock, par value (in dollars per share) \| $ / shares				$ 0.01		$ 0.01	$ 0.01
Preferred stock, shares issued (in shares)				3,000,000		3,000,000	3,000,000
Preferred stock, shares outstanding (in shares)				3,000,000		3,000,000	3,000,000
Preferred stock, cumulative redeemable dividend rate				7.75%		7.75%
Preferred stock, liquidation preference per share (in dollars per share) \| $ / shares				$ 25		$ 25	$ 25
Redemption term				120 days
Redemption price (in dollars per share) \| $ / shares				$ 25.00			$ 25.00
Series C Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)				6,600,000		4,140,000	6,600,000
Preferred stock, par value (in dollars per share) \| $ / shares				$ 0.01		$ 0.01	$ 0.01
Preferred stock, shares issued (in shares)				3,600,000		3,600,000	3,600,000
Preferred stock, shares outstanding (in shares)				3,600,000		3,600,000	3,600,000
Preferred stock, cumulative redeemable dividend rate				7.875%		7.875%
Preferred stock, liquidation preference per share (in dollars per share) \| $ / shares				$ 25		$ 25	$ 25
Preferred stock, shares authorized but unissued									2,460,000
Redemption term				120 days
Redemption price (in dollars per share) \| $ / shares				$ 25.00			$ 25.00
Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)				8,400,000		5,750,000	8,400,000
Preferred stock, par value (in dollars per share) \| $ / shares				$ 0.01		$ 0.01	$ 0.01
Preferred stock, shares issued (in shares)				5,400,000		5,400,000	5,400,000
Preferred stock, shares outstanding (in shares)				5,400,000		5,400,000	5,400,000
Preferred stock, cumulative redeemable dividend rate				8.00%		8.00%	8.00%
Preferred stock, liquidation preference per share (in dollars per share) \| $ / shares				$ 25		$ 25	$ 25				$ 25
Preferred stock, shares authorized but unissued									2,650,000
Redemption term				120 days
Redemption price (in dollars per share) \| $ / shares				$ 25.00			$ 25.00
Series B, Series C and Series D Preferred Stock
Class of Stock [Line Items]
Number of quarters with no dividends that results in voting rights \| quarter				6			6
Number of elected directors pending preferred stock voting rights \| director				2			2
Stockholders required for term changes, percentage				66.67%			66.67%
LIBOR \| Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, cumulative redeemable dividend rate							5.695%