Variable Interest Entities (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2021 USD ($) ft²	Dec. 31, 2019 USD ($) ft²	Mar. 31, 2022 USD ($) ft²	Mar. 31, 2021 USD ($)
Variable Interest Entities [Line Items]
Rentable square feet of office property under development (in sq feet) | ft²			600,000
Assets and liabilities of consolidated variable interest entity [Abstract]
Net real estate assets	$ 5,032,033,000		$ 5,004,488,000
Cash and cash equivalents	23,152,000		18,669,000	$ 49,279,000
Accounts receivable	14,002,000		17,888,000
Accrued straight-line rents receivable	268,324,000		275,133,000
Deferred leasing costs, net	258,902,000		252,207,000
Prepaid expense and other assets, net	78,551,000		81,153,000
Accounts payable, accrued expenses and other liabilities	$ 294,976,000		250,128,000
Variable Interest Entity, Non Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Rentable square feet of office property under development (in sq feet) | ft²	135,000
Total anticipated development costs	$ 79,000,000
Contribution of cash to acquire interest in joint venture	$ 13,300,000
Interest in joint venture (in hundredths)	50.00%
Advance to affiliate	$ 49,600,000
Amount of loan funded to affiliate			0
Term of optional extension	1 year
Risk of loss limited to carrying value			13,500,000
Variable Interest Entity, Non Primary Beneficiary [Member] | London Interbank Offered Rate (LIBOR) [Member]
Variable Interest Entities [Line Items]
Variable interest rate basis	LIBOR
Interest rate, basis spread (in hundredths)	3.00%
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Rentable square feet of office property under development (in sq feet) | ft²		150,000
Total anticipated development costs		$ 71,300,000
Contribution of cash to acquire interest in joint venture		$ 20,000,000
Interest in joint venture (in hundredths)		80.00%
Advance to affiliate		$ 46,300,000
Amount of loan funded to affiliate			30,100,000
Assets and liabilities of consolidated variable interest entity [Abstract]
Net real estate assets	$ 53,191,000		55,061,000
Cash and cash equivalents	389,000		885,000
Accounts receivable	0		229,000
Accrued straight-line rents receivable	121,000		145,000
Deferred leasing costs, net	1,519,000		1,511,000
Prepaid expense and other assets, net	163,000		172,000
Accounts payable, accrued expenses and other liabilities	646,000		$ 1,728,000
Variable Interest Entity, Primary Beneficiary [Member] | London Interbank Offered Rate (LIBOR) [Member]
Variable Interest Entities [Line Items]
Variable interest rate basis		LIBOR
Interest rate, basis spread (in hundredths)		2.50%
Variable Interest Entity, Partner Interest [Member]
Variable Interest Entities [Line Items]
Partner's interest in joint venture (in hundredths)			20.00%
Variable Interest Entity, Partner Interest [Member] | Variable Interest Entity, Non Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Contribution of cash to acquire interest in joint venture	5,600,000
Partner's contribution of property to acquire interest in joint venture	$ 7,700,000
Partner's interest in joint venture (in hundredths)	50.00%
Variable Interest Entity, Partner Interest [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Partner's contribution of property to acquire interest in joint venture		$ 5,000,000
Partner's interest in joint venture (in hundredths)		20.00%