Convertible Debt Instrument, Conversion Ratio, Principal Amount, Basis

No definition available.

Name:	nhi_ConvertibleDebtInstrumentConversionRatioPrincipalAmountBasis
Namespace Prefix:	nhi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of current revolving borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

No definition available.

+ Details

Name:	nhi_CreditFacilityCurrentRevolvingBorrowingCapacity
Namespace Prefix:	nhi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This item represents the contractual minimum for a variable rate basis such as LIBOR for a debt instrument.

+ References

No definition available.

+ Details

Name:	nhi_DebtInstrumentVariableRateBasisMinimum
Namespace Prefix:	nhi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This item represents the net book value of real estate pledged toward mortgage.

+ References

No definition available.

+ Details

Name:	nhi_NetBookValueofRealEstatePledgedTowardMortgage
Namespace Prefix:	nhi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This concept represents the outstanding balance of term loans.

+ References

No definition available.

+ Details

Name:	nhi_TermLoansOutstandingBalance
Namespace Prefix:	nhi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase (decrease) in additional paid in capital (APIC) resulting from recognition of deferred taxes for convertible debt with a beneficial conversion feature.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 55
-Paragraph 51
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

+ Details

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

- Definition

Fair value of all liability derivatives designated as cash flow hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959

+ Details

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

- Definition

Net fair value of all derivative instruments designated as cash flow hedging instruments, which is ordinarily reflected within other comprehensive income.

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-Publisher FASB
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-SubTopic 10
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-Paragraph 5
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying amount of debt identified as being convertible into another form of financial instrument (typically the entity's common stock) as of the balance sheet date, which originally required full repayment more than twelve months after issuance or greater than the normal operating cycle of the company.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The price per share of the conversion feature embedded in the debt instrument.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
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+ Details

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

- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

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-Publisher FASB
-Name Accounting Standards Codification
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Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount by which the convertible debt's if-converted value exceeds its principle amount at the balance sheet date, regardless of whether the instrument is currently convertible. This element applies to public companies only.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of equity instruments that the holder of the debt instrument would receive if the debt was converted to equity.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-Subparagraph (SX 210.5-02.22(a)(5))
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Name:	us-gaap_DebtInstrumentConvertibleNumberOfEquityInstruments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
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+ Details

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

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount.

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-Name Accounting Standards Codification
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-SubTopic 30
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+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
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-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12355-112629

+ Details

Name:	us-gaap_GainsLossesOnExtinguishmentOfDebt
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

For a debtor, the aggregate gain (loss) recognized on the restructuring of payables arises from the difference between the book value of the debt before the restructuring and the fair value of the payments on the debt after restructuring is complete.

+ References

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible debt securities using the if-converted method.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Balance Type:	na
Period Type:	duration

- Definition

The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Paragraph 1
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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

- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

+ Details

Name:	us-gaap_LongTermDebtPercentageBearingFixedInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of the contractual principal due at the origination of the mortgage loan (face amount).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29)
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The stated interest rate on the mortgage loan receivable or the weighted average interest rate on a group of loans.

+ References

+ Details

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

- Definition

Indicates the number of mortgages under each classification.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of debt that an Entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Dividend or interest rate associated with the financial or equity instrument issued as noncash or part noncash consideration for a business or asset acquired. Noncash are transactions that affect recognized assets or liabilities but that do not result in cash receipts or cash payments. Part noncash refers to that portion of the transaction not resulting in cash receipts or cash payments.

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Balance Type:	na
Period Type:	duration

- Definition

The total amount of [all] liabilities that an Entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

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Name:	us-gaap_NoncashOrPartNoncashAcquisitionValueOfLiabilitiesAssumed1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of cash outflow for cost from early extinguishment and prepayment of debt. Includes, but is not limited to, third-party cost, premium paid, and other fee paid to lender directly for debt extinguishment or debt prepayment. Excludes accrued interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

+ References

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Balance Type:	credit
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- Definition

The cash inflow from the issuance of a long-term debt instrument which can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Section 45
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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

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Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
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Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
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Debt (Narrative) (Details)	9 Months Ended	12 Months Ended
Debt (Narrative) (Details)	Sep. 30, 2017	Dec. 31, 2017 USD ($) properties shares number_of_loans $ / shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Mar. 31, 2014 USD ($)
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net		$ 775,000
Loss on extinguishment of debt		(2,214,000)	$ 0	$ 0
Debt Instrument, Unamortized Discount		4,039,000
Line of Credit Facility, Maximum Borrowing Capacity		800,000,000
Credit Facility, Current Revolving Borrowing Capacity		550,000,000
Gains (Losses) on Restructuring of Debt		(583,000)	0	0
Write-off of debt issuance costs		$ 3,592,000	$ 3,514,000	$ 3,413,000
Debt Instrument, Variable Rate Basis, Minimum	0.00%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		2000.00%
Number of Real Estate Properties \| properties		209
Debt Instrument, Convertible, Conversion Ratio		14.23
Convertible Debt Instrument, Conversion Ratio, Principal Amount, Basis		$ 1,000
Debt Instrument, Convertible, Conversion Price \| $ / shares		$ 70.25
Debt Instrument, Convertible, If-converted Value in Excess of Principal		$ 10,776,000
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities \| shares		189,531	89,471	4,735
Debt Instrument, Convertible, Number of Equity Instruments \| shares		2,100,700
Convertible Debt		$ 144,938,000	$ 195,283,000
Debt Instrument, Convertible, Carrying Amount of Equity Component					$ 7,762,000
Debt Instrument, Interest Rate, Effective Percentage		3.90%
Payments of Debt Issuance Costs		$ 4,935,000	258,000	$ 2,608,000
Unamortized Debt Issuance Expense		10,453,000	9,740,000
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed		1,855,000	430,000	$ 1,076,000
Bank Term Loans [Member]
Unsecured Debt		250,000,000	250,000,000
Debt Instrument, Basis Spread on Variable Rate	13000.00%
Term Loans, Outstanding Balance		250,000,000
Original Amount [Member]
Convertible Debt		192,238,000
Private Placement [Member]
Unsecured Debt		400,000,000	400,000,000
Debt Instrument, Name, Revolving Credit Facility [Member]
Write-off of debt issuance costs		$ 407,000
Debt Instrument, Basis Spread on Variable Rate		11500.00%
Unused balance of the unsecured revolving credit facility		$ 329,000,000
FNMA Berkadia Note [Member]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		4.60%
Debt Instrument, Name, Convertible Senior Notes [Member]
Payment for Debt Extinguishment or Debt Prepayment Cost		$ 50,777,000
Loss on extinguishment of debt		2,214,000
Adjustments to Additional Paid in Capital, Convertible Debt with Conversion Feature		7,930,000
Debt Instrument, Unamortized Discount		$ 2,637,000	4,717,000
Debt Instrument, Interest Rate, Stated Percentage		3.25%
Debt Instrument, Face Amount		$ 147,575,000
Payments of Debt Issuance Costs		6,063,000
Unamortized Debt Issuance Expense		1,752,000
At Inception [Member]
Proceeds from Convertible Debt		$ 200,000,000
Debt Instrument, Convertible, Conversion Ratio		13.93
Debt Instrument, Convertible, Conversion Price \| $ / shares		$ 71.81
Debt Instrument, Convertible, Number of Equity Instruments \| shares		2,785,200
Debt Instrument, Name, HUD Mortgages [Member]
Number of Real Estate Properties \| properties		10
Net Book Value of Real Estate Pledged Toward Mortgage		$ 52,586,000
Debt Instrument, HUD Mortgages, 2049 Maturity [Member]
Mortgage Loans on Real Estate, Number of Loans \| number_of_loans		9
Debt Instrument, Name, Fannie Mae Term Loans [Member]
Debt Instrument, Term		10 years
Mortgage Loans on Real Estate, Face Amount of Mortgages		$ 78,084,000
Debt Instrument, Interest Rate, Stated Percentage		3.79%
Number of Real Estate Properties		13
Net Book Value of Real Estate Pledged Toward Mortgage		$ 142,258,000
Debt Instrument, Name, Q3 2014 HUD Mortgages [Member]
Debt Instrument, Unamortized Discount		$ 1,402,000	1,487,000
Debt Instrument, HUD Mortgages, 2047 Maturity [Member]
Mortgage Loans on Real Estate, Number of Loans \| number_of_loans		1
Allocated to Debt [Member] \| Debt Instrument, Name, Convertible Senior Notes [Member]
Payments of Debt Issuance Costs		$ 5,788,000
Allocated to Equity [Member] \| Debt Instrument, Name, Convertible Senior Notes [Member]
Payments of Debt Issuance Costs		$ 275,000
Bickford Senior Living [Member]
Number of Real Estate Properties \| properties		47
Middletown, OH [Member] \| Bickford Senior Living [Member]
Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Rate		2.90%
Noncash or Part Noncash Acquisition, Debt Assumed		$ 8,911,000
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed		$ 7,509,000
Minimum [Member] \| Debt Instrument, Name, HUD Mortgages [Member]
Mortgage Loans on Real Estate, Interest Rate		4.30%
Maximum [Member] \| Debt Instrument, Name, HUD Mortgages [Member]
Mortgage Loans on Real Estate, Interest Rate		4.40%
Fair Value, Inputs, Level 2 [Member]
Cash Flow Hedges Derivative Instruments at Fair Value, Net		$ (588,000)
Cash Flow Hedge Derivative Instrument Liabilities at Fair Value		747,000	$ 4,279,000
November 2025 [Member] \| Private Placement [Member]
Unsecured Debt		$ 50,000,000
Debt Instrument, Interest Rate, Stated Percentage		4.33%