As of the balance sheet date: carrying value of obligations incurred and payable pertaining to goods and services received from vendors; and for statutory costs, are incurred in connection with contractual obligations, or accumulate over time and for which invoices haven't been received or rendered; and carrying amount of liabilities not otherwise specified in the taxonomy. Also serves as the sum of liabilities not individually reported in the financial statements, or not separately disclosed in notes.

No definition available.

Consolidated Variable Interest Entity (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) ft²	Mar. 31, 2021 USD ($) ft²	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)
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]
Development in-process		$ 288,406	$ 259,681
Cash and cash equivalents		49,279	109,322	$ 12,696
Deferred leasing costs		219,790	209,329
Prepaid expense and other assets		72,845	62,885
Accounts payable, accrued expenses and other liabilities		258,026	$ 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		21,100
Assets and liabilities of consolidated variable interest entity [Abstract]
Development in-process		49,039
Cash and cash equivalents		85
Deferred leasing costs		196
Prepaid expense and other assets		127
Accounts payable, accrued expenses and other liabilities		$ 2,127
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%