Debt (Narrative) (Details)	12 Months Ended
Dec. 31, 2018 USD ($) properties shares number_of_loans $ / shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares
Derivative, Fair Value, Net	$ 1,297,000	$ (588,000)
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	963,000
Loss on extinguishment of debt	(738,000)	(2,214,000)	$ 0
Debt Instrument, Unamortized Discount	2,711,000
Unsecured Debt	400,000,000
Credit Facility, Current Revolving Borrowing Capacity	550,000,000
Gains (Losses) on Restructuring of Debt	$ 0	$ (583,000)	0
Debt Instrument, Variable Rate Basis, Minimum	25198.80%	15642.50%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	2000.00%
Number of Real Estate Properties \| properties	220
Debt Instrument, Convertible, Conversion Ratio	14.42
Debt Instrument, Convertible, Conversion Price \| $ / shares	$ 69.36
Debt Instrument, Convertible, If-converted Value in Excess of Principal	$ 10,697,000
Loss on Cash Flow Hedge Ineffectiveness	0	$ (353,000)	$ (18,000)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ 235,000
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities \| shares	80,123	189,531	89,471
Debt Instrument, Convertible, Number of Equity Instruments \| shares	1,730,174
Payments for Repurchase of Redeemable Convertible Preferred Stock	$ 29,985,000	$ 60,921,000	$ 0
Repayments of Convertible Debt	27,558,000
Convertible Debt	118,609,000	144,938,000
Payments of Debt Issuance Costs	2,171,000	4,935,000	258,000
Unamortized Debt Issuance Expense	9,884,000	10,453,000
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed	1,689,000	1,855,000	$ 430,000
$300M Term Loan [Member]
Term Loans, Outstanding Balance	300,000,000
Bank Term Loans [Member]
Unsecured Debt	$ 550,000,000	250,000,000
Debt Instrument, Basis Spread on Variable Rate	12700.00%
Term Loans, Outstanding Balance	$ 250,000,000
Private Placement [Member]
Unsecured Debt	$ 400,000,000	400,000,000
Debt Instrument, Name, Revolving Credit Facility [Member]
Debt Instrument, Basis Spread on Variable Rate	11500.00%
Unused balance of the unsecured revolving credit facility	$ 466,000,000
FNMA Berkadia Note [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Face Amount of Mortgages	$ 17,960,000
Debt Instrument, Interest Rate, Stated Percentage	4.60%
Debt Instrument, Name, Convertible Senior Notes [Member]
Loss on extinguishment of debt	$ 738,000
Adjustments to Additional Paid in Capital, Convertible Debt with Conversion Feature	2,427,000
Debt Instrument, Unamortized Discount	$ 1,391,000	2,637,000
Debt Instrument, Interest Rate, Stated Percentage	3.25%
Convertible Debt Instrument, Conversion Ratio, Principal Amount, Basis	$ 1,000
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	$ 50,867,000
Debt Instrument, HUD Mortgages, 2049 Maturity [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in 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
SEC Schedule, 12-29, Real Estate Companies, Investment in 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	$ 138,273,000
Debt Instrument, Name, Q3 2014 HUD Mortgages [Member]
Debt Instrument, Unamortized Discount	$ 1,320,000	1,402,000
Debt Instrument, HUD Mortgages, 2047 Maturity [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Number of Loans \| number_of_loans	1
Bickford Senior Living [Member]
Number of Real Estate Properties \| properties	52
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	$ 8,705,000
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed	$ 7,385,000
Minimum [Member] \| Debt Instrument, Name, HUD Mortgages [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Interest Rate	4.30%
Maximum [Member] \| Debt Instrument, Name, HUD Mortgages [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Interest Rate	4.40%
Fair Value, Inputs, Level 2 [Member]
Cash Flow Hedge Derivative Instrument Liabilities at Fair Value	$ 0	$ 747,000
November 2025 [Member]
Unsecured Debt	$ 50,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.33%

Convertible Debt Instrument, Conversion Ratio, Principal Amount, Basis

No definition available.

Name:	nhi_ConvertibleDebtInstrumentConversionRatioPrincipalAmountBasis
Namespace Prefix:	nhi_
Data Type:	xbrli:monetaryItemType
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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.

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- Definition

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

+ References

No definition available.

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Namespace Prefix:	nhi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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Namespace Prefix:	nhi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

This concept represents the outstanding balance of term loans.

+ References

No definition available.

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- Definition

Amount of contractual principal due at origination of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

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-Publisher SEC
-Name Regulation S-X (SX)
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-Section 12
-Paragraph Column F
-Subsection 29

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-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column F))
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- Definition

Interest rate of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

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-Publisher SEC
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Number of mortgage loans within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

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-Publisher SEC
-Name Regulation S-X (SX)
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- 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.

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

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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.

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

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No definition available.

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

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- Definition

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

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- 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.

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

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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.

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Amount, after accumulated amortization, of debt discount.

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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-Paragraph 10
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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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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.

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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.

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

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

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No definition available.

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The loss recognized in earnings during the reporting period representing the amount of the cash flow hedges' ineffectiveness.

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Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

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