Fair Value Measurements - Narratives (Details) $ / shares in Units, $ in Thousands	1 Months Ended					3 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2023 property	Oct. 31, 2022 USD ($)	Aug. 31, 2022 property	Mar. 31, 2022 property	Jan. 31, 2022 USD ($) $ / shares shares	Sep. 30, 2023 USD ($) property shares	Sep. 30, 2022 USD ($) property	Sep. 30, 2023 USD ($) property shares	Sep. 30, 2022 USD ($) property	Dec. 31, 2022 USD ($) property shares
Fair Value Inputs, Assets
Equity method investments in real estate						$ 351,537		$ 351,537		$ 327,502
Preferred stock, shares issued (in shares) | shares						0		0		0
Proceeds from issuance of preferred stock								$ 0	$ 65,000
Goodwill impairment						$ 0	$ 29,334	$ 0	29,334
Investment Management
Fair Value Inputs, Assets
Goodwill impairment							29,300		29,300
Goodwill, fair value							0		0
Asset Held for Sale, Not in Discontinued Operations
Fair Value Inputs, Assets
Number of real estate properties (property) | property						8		8		3
Real estate and intangibles | Pendragon PLC
Fair Value Inputs, Assets
Number of real estate properties (property) | property				30
Lease extension term (in years)				11 years
Real estate and intangibles | Pendragon PLC | Asset Held for Sale, Not in Discontinued Operations
Fair Value Inputs, Assets
Number of real estate properties (property) | property				12
Number of properties sold | property										4
Watermark Lodging Trust
Fair Value Inputs, Assets
Cash proceeds		$ 82,600
GCIF
Fair Value Inputs, Assets
Proceeds from liquidation distribution								$ 800
Equity method investments in real estate						$ 900		900		$ 1,700
Affiliated Entity | Common Stock | Watermark Lodging Trust
Fair Value Inputs, Assets
Shares owned (in shares) | shares					12,208,243
Level 3 | Fair Value, Measurements, Nonrecurring
Fair Value Inputs, Assets
Recognized impairment costs						15,173	29,334	15,173	55,719
Level 3 | Real estate and intangibles | Fair Value, Measurements, Nonrecurring
Fair Value Inputs, Assets
Recognized impairment costs						$ 15,173	$ 0	$ 15,173	26,385
Number of real estate properties (property) | property						1		1
Level 3 | Real estate and intangibles | Fair Value, Measurements, Nonrecurring | Pendragon PLC | Asset Held for Sale, Not in Discontinued Operations
Fair Value Inputs, Assets
Recognized impairment costs									$ 9,300
Number of real estate properties (property) | property							6		6
Level 3 | Real estate and intangibles | Fair Value, Measurements, Nonrecurring | Pendragon PLC | Asset Held for Sale, Not in Discontinued Operations | Terminal Capitalization Rate | Minimum
Fair Value Inputs, Assets
Capitalization rate for the various scenarios (as a percent)							0.0475		0.0475
Level 3 | Real estate and intangibles | Fair Value, Measurements, Nonrecurring | Pendragon PLC | Asset Held for Sale, Not in Discontinued Operations | Terminal Capitalization Rate | Maximum
Fair Value Inputs, Assets
Capitalization rate for the various scenarios (as a percent)							0.1000		0.1000
Level 3 | Potentially Vacant Properties | Building | Fair Value, Measurements, Nonrecurring
Fair Value Inputs, Assets
Recognized impairment costs									$ 10,900
Level 3 | Potentially Vacant Properties | Building | Fair Value, Measurements, Nonrecurring | Cashflow Discount Rate
Fair Value Inputs, Assets
Capitalization rate for the various scenarios (as a percent)							0.140		0.140
Level 3 | Potentially Vacant Properties | Building | Fair Value, Measurements, Nonrecurring | Terminal Capitalization Rate
Fair Value Inputs, Assets
Capitalization rate for the various scenarios (as a percent)							0.110		0.110
Level 3 | Two Properties | Real estate and intangibles | Fair Value, Measurements, Nonrecurring
Fair Value Inputs, Assets
Recognized impairment costs									$ 6,200
Number of real estate properties (property) | property							2		2
Number of properties sold | property	1		1
Lineage Logistics | Level 3
Fair Value Inputs, Assets
Dividend income									$ 4,300
Fair value of investments						$ 404,900		$ 404,900		$ 404,900
Watermark Lodging Trust
Fair Value Inputs, Assets
Preferred stock, shares issued (in shares) | shares					1,300,000
Reclassification of unrealized gain on investments to net income									43,400
Watermark Lodging Trust | Affiliated Entity
Fair Value Inputs, Assets
Proceeds from issuance of preferred stock					$ 65,000
Preferred stock liquidation preference (in dollars per share) | $ / shares					$ 50.00
Reclassification of unrealized gain on investments to net income					$ 18,700
Watermark Lodging Trust | Level 3
Fair Value Inputs, Assets
Dividend income									$ 900