Subsequent Events (Details)		1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Nov. 01, 2023 USD ($) property	Oct. 31, 2023 USD ($) loan property $ / shares shares	Sep. 30, 2023 USD ($) property	Sep. 30, 2022 USD ($) property	Sep. 30, 2023 USD ($) property	Sep. 30, 2022 USD ($) property	Dec. 31, 2022 USD ($) property	Mar. 31, 2023 property
Subsequent Event
Maximum borrowing capacity							$ 2,750,000,000
Proceeds from sales of real estate					$ 187,678,000	$ 170,341,000
Repayments of secured loans					$ 251,028,000	$ 51,548,000
Owned Real Estate Segment [Member]
Subsequent Event
Number of real estate properties (property) | property			1,472		1,472
Net Lease Office Properties | Line of Credit
Subsequent Event
Maximum borrowing capacity			$ 455,000,000		$ 455,000,000
Spinoff
Subsequent Event
Spin-off costs					61,600,000
Advisory fees					5,100,000		$ 4,900,000
Additional spin-off related costs			$ 51,600,000		$ 51,600,000
Spinoff | Office Property
Subsequent Event
Number of real estate properties (property) | property			59		59
Properties Disposed of by Sale
Subsequent Event
Number of real estate properties (property) | property								2
Number of properties sold | property			6	3	14	17
Proceeds from sales of real estate			$ 143,600,000	$ 55,200,000	$ 187,700,000	$ 170,300,000
Asset Held for Sale, Not in Discontinued Operations
Subsequent Event
Number of real estate properties (property) | property			8		8		3
Asset Held for Sale, Not in Discontinued Operations | Owned Real Estate Segment [Member]
Subsequent Event
Number of real estate properties (property) | property			6		6
Asset Held for Sale, Not in Discontinued Operations | Hotel | Owned Real Estate Segment [Member]
Subsequent Event
Number of real estate properties (property) | property			3		3
Subsequent Events
Subsequent Event
Loans repaid count | loan		2
Repayments of secured loans		$ 41,300,000
Subsequent Events | ATM Program
Subsequent Event
Net proceeds		$ 384,000,000
Subsequent Events | Net Lease Office Properties | Line of Credit
Subsequent Event
Maximum borrowing capacity	$ 350,000,000
Subsequent Events | Net Lease Office Properties
Subsequent Event
Management fee payable	7,500,000
Administrative fee income	4,000,000
Subsequent Events | Common Stock | ATM Program
Subsequent Event
Issued (in shares) | shares		4,744,973
Sale of stock, price (usd per share) | $ / shares		$ 80.95
Subsequent Events | Spinoff
Subsequent Event
Advisory fees	$ 10,000,000
Subsequent Events | Spinoff | Office Property
Subsequent Event
Number of real estate properties (property) | property	59	59
Number of properties sold | property	3
Subsequent Events | Properties Disposed of by Sale
Subsequent Event
Number of properties sold | property		7
Proceeds from sales of real estate		$ 101,900,000