Subsequent Events (Details) $ in Millions		3 Months Ended
	Jul. 29, 2021 USD ($) ft²	Sep. 30, 2021 USD ($)	Jun. 30, 2021 ft²
Subsequent Event [Line Items]
Area of real estate property (in square feet)			10,100,000
Forecast
Subsequent Event [Line Items]
Straight line rent receivables written-off | $		$ 1.6
Subsequent Event
Subsequent Event [Line Items]
Letter of credit converted to cash | $	$ 17.0
Subsequent Event | Subsidiaries | GBG USA Inc.
Subsequent Event [Line Items]
Area of real estate property (in square feet)	353,325
Proportion of rentable square feet in total portfolio (as a percent)	3.50%
Proportion of annualized rent in total portfolio (as a percent)	3.60%
Area of real estate property that was not sublet to tenants (in square feet)	191,000
Proportion of rentable square feet in total portfolio that was not sublet to tenants (as a percent)	1.90%