Investment Securities Available for Sale, at Fair Value - Proceeds from Sale (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds	$ 61,832	$ 1,445,196	$ 56,769
Realized Gains	1,621	12,689	16,957
Realized Losses	(1,690)	(71,468)	(156)
Net Realized Gains/Losses	(69)	(58,779)	16,801
Agency RMBS
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds		992,966
Realized Gains		5,402
Realized Losses		(15,854)
Net Realized Gains/Losses		(10,452)
Agency RMBS \| Agency ARMs
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds		49,892
Realized Gains		44
Realized Losses		(4,157)
Net Realized Gains/Losses		(4,113)
Agency RMBS \| Agency Fixed- Rate
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds		943,074
Realized Gains		5,358
Realized Losses		(11,697)
Net Realized Gains/Losses		(6,339)
Agency CMBS
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds		145,411
Realized Gains		5,666
Realized Losses		(209)
Net Realized Gains/Losses		5,457
Total Agency
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds		1,138,377
Realized Gains		11,068
Realized Losses		(16,063)
Net Realized Gains/Losses		(4,995)
Non-Agency RMBS
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds	37,810	168,758
Realized Gains	294	294
Realized Losses	(1,690)	(25,821)
Net Realized Gains/Losses	(1,396)	(25,527)
Non-Agency RMBS \| Non-Agency RMBS Held in Securitization Trust
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds	27,200	27,200
Net Realized Gains/Losses	200	200
CMBS
Debt Securities, Available-for-sale [Line Items]
Sales Proceeds	24,022	138,061	56,769
Realized Gains	1,327	1,327	16,957
Realized Losses	0	(29,584)	(156)
Net Realized Gains/Losses	$ 1,327	$ (28,257)	$ 16,801

Proceeds Including Receivable For Unsettled Trades From Sale of Debt Securities, Available-for-sale

No definition available.

Name:	nymt_ProceedsIncludingReceivableForUnsettledTradesFromSaleofDebtSecuritiesAvailableforsale
Namespace Prefix:	nymt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27357-111563

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleRealizedGain
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27357-111563

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

+ Details

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

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=nymt_AgencyResidentialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=nymt_AgencyARMsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=nymt_AgencyFixedRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=nymt_AgencyCMBSMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_AgencySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=nymt_NonAgencyRMBSMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=nymt_NonAgencyRMBSHeldinSecuritizationTrustMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=nymt_CMBSMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: