Consolidated Variable Interest Entity (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) ft²	Jun. 30, 2021 USD ($) ft²	Dec. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)
Consolidated Variable Interest Entity [Abstract]
Rentable square feet of office property under development (in sq feet) | ft²		800,000
Assets and liabilities of consolidated variable interest entity [Abstract]
Net real estate assets		$ 4,548,909	$ 4,421,285
Cash and cash equivalents		6,535	109,322	$ 4,752
Deferred leasing costs		216,318	209,329
Prepaid expense and other assets, net of accumulated depreciation		127,853	62,885
Accounts payable, accrued expenses and other liabilities		265,296	$ 268,727
Consolidated Variable Interest Entity [Member]
Consolidated Variable Interest Entity [Abstract]
Rentable square feet of office property under development (in sq feet) | ft²	150,000
Total anticipated development costs	$ 71,300
Contribution of cash to acquire interest in consolidated joint venture	$ 20,000
Interest in consolidated joint venture (in hundredths)	80.00%
Partner's contribution of property to acquire interest in consolidated joint venture	$ 5,000
Advance to consolidated affiliate	$ 46,300
Amount of loan funded to affiliate		23,700
Assets and liabilities of consolidated variable interest entity [Abstract]
Net real estate assets		51,533
Cash and cash equivalents		101
Deferred leasing costs		260
Prepaid expense and other assets, net of accumulated depreciation		126
Accounts payable, accrued expenses and other liabilities		$ 1,798
Consolidated Variable Interest Entity [Member] | London Interbank Offered Rate (LIBOR) [Member]
Consolidated Variable Interest Entity [Abstract]
Variable interest rate basis	LIBOR
Interest rate, basis spread (in hundredths)	2.50%
Variable Interest Entity [Member]
Consolidated Variable Interest Entity [Abstract]
Partner's interest in consolidated joint venture (in hundredths)		20.00%
Variable Interest Entity [Member] | Consolidated Variable Interest Entity [Member]
Consolidated Variable Interest Entity [Abstract]
Partner's interest in consolidated joint venture (in hundredths)	20.00%