Secured and unsecured senior debt (Tables)

12 Months Ended

Dec. 31, 2023

Schedule of maturities of secured and unsecured debt

The following table summarizes our outstanding indebtedness and respective principal payments as of December 31, 2023 (dollars in thousands):


	Stated Rate		Interest Rate (1)			Maturity Date (2)		Principal Payments Remaining for the Periods Ending December 31,															Unamortized (Deferred Financing Cost), (Discount) Premium
Debt								2024		2025		2026		2027		2028		Thereafter			Principal				Total
Secured notes payable
Greater Boston(3)	SOFR+2.70	%	8.38	%		11/19/26		$	—	$	—	$	119,674	$	—	$	—	$	—		$	119,674	$	(631)	$	119,043
San Francisco Bay Area	6.50	%	6.50			7/1/36		32		34		36		38		41		438			619		—		619
Secured debt weighted-average interest rate/subtotal			8.37					32		34		119,710		38		41		438			120,293		(631)		119,662

Unsecured senior line of credit and commercial paper program(4)	(4)		5.76		(4)	1/22/28	(4)	(4)		—		—		—		100,000		—		(4)	100,000		(48)		99,952
Unsecured senior notes payable	3.45	%	3.62			4/30/25		—		600,000		—		—		—		—			600,000		(1,181)		598,819
Unsecured senior notes payable	4.30	%	4.50			1/15/26		—		—		300,000		—		—		—			300,000		(1,022)		298,978
Unsecured senior notes payable	3.80	%	3.96			4/15/26		—		—		350,000		—		—		—			350,000		(1,143)		348,857
Unsecured senior notes payable	3.95	%	4.13			1/15/27		—		—		—		350,000		—		—			350,000		(1,574)		348,426
Unsecured senior notes payable	3.95	%	4.07			1/15/28		—		—		—		—		425,000		—			425,000		(1,733)		423,267
Unsecured senior notes payable	4.50	%	4.60			7/30/29		—		—		—		—		—		300,000			300,000		(1,248)		298,752
Unsecured senior notes payable	2.75	%	2.87			12/15/29		—		—		—		—		—		400,000			400,000		(2,473)		397,527
Unsecured senior notes payable	4.70	%	4.81			7/1/30		—		—		—		—		—		450,000			450,000		(2,425)		447,575
Unsecured senior notes payable	4.90	%	5.05			12/15/30		—		—		—		—		—		700,000			700,000		(5,511)		694,489
Unsecured senior notes payable	3.375	%	3.48			8/15/31		—		—		—		—		—		750,000			750,000		(4,990)		745,010
Unsecured senior notes payable	2.00	%	2.12			5/18/32		—		—		—		—		—		900,000			900,000		(7,887)		892,113
Unsecured senior notes payable	1.875	%	1.97			2/1/33		—		—		—		—		—		1,000,000			1,000,000		(7,976)		992,024
Unsecured senior notes payable	2.95	%	3.07			3/15/34		—		—		—		—		—		800,000			800,000		(7,989)		792,011
Unsecured senior notes payable	4.75	%	4.88			4/15/35		—		—		—		—		—		500,000			500,000		(5,411)		494,589
Unsecured senior notes payable	4.85	%	4.93			4/15/49		—		—		—		—		—		300,000			300,000		(2,987)		297,013
Unsecured senior notes payable	4.00	%	3.91			2/1/50		—		—		—		—		—		700,000			700,000		10,111		710,111
Unsecured senior notes payable	3.00	%	3.08			5/18/51		—		—		—		—		—		850,000			850,000		(11,608)		838,392
Unsecured senior notes payable	3.55	%	3.63			3/15/52		—		—		—		—		—		1,000,000			1,000,000		(14,112)		985,888
Unsecured senior notes payable	5.15	%	5.26			4/15/53		—		—		—		—		—		500,000			500,000		(7,813)		492,187
Unsecured debt weighted-average interest rate/subtotal			3.67					—		600,000		650,000		350,000		525,000		9,150,000			11,275,000		(79,020)		11,195,980
Weighted-average interest rate/total			3.72	%				$	32	$	600,034	$	769,710	$	350,038	$	525,041	$	9,150,438		$	11,395,293	$	(79,651)	$	11,315,642

(1)Represents the weighted-average interest rate as of the end of the applicable period, including amortization of loan fees, amortization of debt premiums (discounts), and other bank fees.

(2)Reflects any extension options that we control.

(3)Represents a secured construction loan held by our consolidated real estate joint venture at 99 Coolidge Avenue, of which we own a 75.0% interest. As of December 31, 2023, this joint venture has $75.6 million available under existing lender commitments. The interest rate shall be reduced from SOFR+2.70% to SOFR+2.10% over time upon the completion of certain leasing, construction, and financial covenant milestones.

(4)Refer to “$5.0 billion unsecured senior line of credit” and “$2.5 billion commercial paper program” on the following page.

Summary of secured and unsecured debt

The following table summarizes our secured and unsecured senior debt and amounts outstanding under our unsecured senior line of credit and commercial paper program as of December 31, 2023 (dollars in thousands):


	Fixed-Rate Debt			Variable-Rate Debt									Weighted-Average
													Interest Rate(1)			Remaining Term (in years)
							Total				Percentage
Secured notes payable	$	619		$	119,043		$	119,662			1.1	%	8.37	%		2.9
Unsecured senior notes payable	11,096,028			—			11,096,028				98.0		3.65			13.0
Unsecured senior line of credit and commercial paper program	—			99,952			99,952			(2)	0.9		5.76		(2)	4.1	(3)
Total/weighted average	$	11,096,647		$	218,995		$	11,315,642			100.0	%	3.72	%		12.8	(3)
Percentage of total debt	98.1		%	1.9		%	100		%

(1)Represents the weighted-average interest rate as of the end of the applicable period, including expense/income related to the amortization of loan fees, amortization of debt premiums (discounts), and other bank fees.

(2)As of December 31, 2023, we had no outstanding balance on our unsecured senior line of credit and $100.0 million of commercial paper notes outstanding.

(3)We calculate the weighted-average remaining term of our commercial paper notes by using the maturity date of our unsecured senior line of credit. Using the maturity date of our outstanding commercial paper notes, the consolidated weighted-average maturity of our debt is 12.7 years. The commercial paper notes sold during the year ended December 31, 2023 were issued at a weighted-average yield to maturity of 5.55% and had a weighted-average maturity term of 11 days.

Schedule of Interest Incurred

The following table summarizes interest expense for the years ended December 31, 2023, 2022, and 2021 (in thousands):


	Year Ended December 31,
	2023		2022		2021
Interest incurred	$	438,182	$	372,848	$	312,806
Capitalized interest	(363,978)		(278,645)		(170,641)
Interest expense	$	74,204	$	94,203	$	142,165