Secured and unsecured senior debt

9 Months Ended

Sep. 30, 2021

Debt Disclosure [Abstract]

Secured and unsecured senior debt

The following table summarizes our outstanding indebtedness and respective principal payments as of September 30, 2021 (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								2021		2022		2023		2024		2025		Thereafter		Principal				Total
Secured notes payable
Greater Boston	4.82	%		3.40	%		2/6/24	$	870	$	3,564	$	3,742	$	183,527	$	—	$	—	$	191,703	$	6,377	$	198,080
San Francisco Bay Area	6.50	%		6.50			7/1/36	—		28		30		32		34		554		678		—		678
Secured debt weighted-average interest rate/subtotal	4.83	%		3.41				870		3,592		3,772		183,559		34		554		192,381		6,377		198,758
Commercial paper program(3)	0.23	%	(3)	0.23		(3)	(3)	(3)		—		—		—		—		750,000		750,000		(22)		749,978
Unsecured senior line of credit	L+0.815	%	(4)	N/A			1/6/26	—		—		—		—		—		—		—		—		—
Unsecured senior notes payable	3.45	%		3.62			4/30/25	—		—		—		—		600,000		—		600,000		(3,151)		596,849
Unsecured senior notes payable	4.30	%		4.50			1/15/26	—		—		—		—		—		300,000		300,000		(2,106)		297,894
Unsecured senior notes payable – green bond	3.80	%		3.96			4/15/26	—		—		—		—		—		350,000		350,000		(2,237)		347,763
Unsecured senior notes payable	3.95	%		4.13			1/15/27	—		—		—		—		—		350,000		350,000		(2,693)		347,307
Unsecured senior notes payable	3.95	%		4.07			1/15/28	—		—		—		—		—		425,000		425,000		(2,673)		422,327
Unsecured senior notes payable	4.50	%		4.60			7/30/29	—		—		—		—		—		300,000		300,000		(1,744)		298,256
Unsecured senior notes payable	2.75	%		2.87			12/15/29	—		—		—		—		—		400,000		400,000		(3,385)		396,615
Unsecured senior notes payable	4.70	%		4.81			7/1/30	—		—		—		—		—		450,000		450,000		(3,259)		446,741
Unsecured senior notes payable	4.90	%		5.05			12/15/30	—		—		—		—		—		700,000		700,000		(7,261)		692,739
Unsecured senior notes payable	3.375	%		3.48			8/15/31	—		—		—		—		—		750,000		750,000		(6,422)		743,578
Unsecured senior notes payable – green bond	2.00	%		2.12			5/18/32	—		—		—		—		—		900,000		900,000		(9,939)		890,061
Unsecured senior notes payable	1.875	%		1.97			2/1/33	—		—		—		—		—		1,000,000		1,000,000		(9,916)		990,084
Unsecured senior notes payable	4.85	%		4.93			4/15/49	—		—		—		—		—		300,000		300,000		(3,246)		296,754
Unsecured senior notes payable	4.00	%		3.91			2/1/50	—		—		—		—		—		700,000		700,000		10,342		710,342
Unsecured senior notes payable	3.00	%		3.08			5/18/51	—		—		—		—		—		850,000		850,000		(12,459)		837,541
Unsecured debt weighted-average interest rate/subtotal				3.27				—		—		—		—		600,000		8,525,000		9,125,000		(60,171)		9,064,829
Weighted-average interest rate/total				3.27	%			$	870	$	3,592	$	3,772	$	183,559	$	600,034	$	8,525,554	$	9,317,381	$	(53,794)	$	9,263,587

(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)Refer to footnote 2 on the next page.

(4)During the year ended December 31, 2020, we achieved certain sustainability measures, as described in our unsecured senior line of credit agreement, which reduced the borrowing rate by one basis point for one year ending December 31, 2021.

Unsecured senior notes payable

In February 2021, we opportunistically issued $1.75 billion of unsecured senior notes payable with a weighted-average interest rate of 2.49% and a weighted-average maturity of 20.4 years. The unsecured senior notes consisted of $900.0 million of 2.00% unsecured senior notes due 2032 (“2.00% Unsecured Senior Notes”) and $850.0 million of 3.00% unsecured senior notes due 2051 (“3.00% Unsecured Senior Notes”). The proceeds from our 2.00% Unsecured Senior Notes are expected to be allocated to eligible green projects and were initially used to refinance $650.0 million of our 4.00% unsecured senior notes payable due in 2024 pursuant to a partial cash tender offer completed on February 10, 2021, and a subsequent call for redemption for the remaining outstanding amounts that settled on March 12, 2021. As a result of this refinancing, we recognized a loss on early extinguishment of debt of $67.2 million, including the write-off of unamortized loan fees and premiums.

$1.5 billion commercial paper program

Our commercial paper program provides us with the ability to issue up to $1.5 billion of commercial paper with a maturity of generally 30 days or less and with a maximum maturity of 397 days from the date of issuance. Our commercial paper program is backed by our unsecured senior line of credit, and at all times we expect to retain a minimum undrawn amount of borrowing capacity under our unsecured senior line of credit equal to any outstanding notes issued under our commercial paper program. We use the net proceeds from the issuances of the notes for general working capital and other general corporate purposes. General corporate purposes may include, but are not limited to, the repayment of other debt and selective development, redevelopment, or acquisition of properties. As of September 30, 2021, we had $750.0 million of notes outstanding under our commercial paper program.

Interest expense

The following table summarizes interest expense for the three and nine months ended September 30, 2021 and 2020 (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Gross interest	$	78,863	$	75,874	$	233,866	$	222,100
Capitalized interest	(43,185)		(32,556)		(126,563)		(88,029)
Interest expense	$	35,678	$	43,318	$	107,303	$	134,071