Investments - Narrative (Details) $ in Millions	3 Months Ended
Mar. 31, 2020 USD ($) State Property loan Note	Dec. 31, 2019 Property
Real Estate Properties [Line Items]
Gross investment in owned real estate properties	$ 6,300.0
Portfolio disbursement, number of states \| State	48
Minimum of investment in real estate properties	10.00%
Number of properties under operating leases \| Property	1,760	1,745
Number of properties under direct financing lease \| Property	1
Sales-type and direct financing leases minimum future payments to be received	$ 4.0
Direct financing leases, reserves for uncollectible amount	0.3
Direct financing leases, net investment balance	$ 7.6
Mortgage Receivables And Other Notes Receivable
Real Estate Properties [Line Items]
Number of other note receivable \| Note	1
Loans outstanding principal balance	$ 30.6
Unamortized premium balance	0.5
Allowance for loan losses	0.3
Loans receivable carrying value	$ 31.1
Single-Tenant Commercial Properties \| First Mortgage \| Mortgage Receivables And Other Notes Receivable
Real Estate Properties [Line Items]
Number of first-priority mortgage loans \| loan	2
Texas
Real Estate Properties [Line Items]
Investment in real estate properties	11.40%

Financing receivable, number of financing receivables.

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Lessor Capital Lease Number Of Properties

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Lessor Operating Lease Number Of Properties

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Minimum Percentage Of Investment In Real Estate Properties Over Which Investment To Be Disclosed

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Number Of States Real Estate Properties Located

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Percentage Of Investment In Real Estate Properties

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Real Estate Investment Property Gross

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
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-Section 12
-Footnote 3
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Present value of lease payments not yet received by lessor and amount expected to be derived from underlying asset, following end of lease term, guaranteed by lessee or other third party unrelated to lessor, from direct financing lease.

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Amount of allowance for credit loss on net investment in direct financing lease.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount, before allowance and fees, of loans and leases receivable. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount of net investment in sales-type and direct financing lease.

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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.

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Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

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