Summary of Significant Accounting Policies - Equity Securities (Details) $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($) shares
Debt and Equity Securities, FV-NI [Line Items]
Distributions in excess of earnings from Affiliates Insurance Company \| $	$ 9,000
Travel Centers of America LLC
Debt and Equity Securities, FV-NI [Line Items]
Number of common shares owned (in shares)	684,000
Travel Centers of America LLC \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Debt and Equity Securities, FV-NI [Line Items]
Number of common shares owned (in shares)	684,000

Balance held at close of period in number of shares.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 50
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-URI http://asc.fasb.org/extlink&oid=99383244&loc=d3e12121-115841

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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