Indebtedness

Our principal debt obligations at December 31, 2018 were: (1) outstanding borrowings under our $1,000,000 unsecured revolving credit facility; (2) seven public issuances of senior unsecured notes, including: (a) $400,000 principal amount at an annual interest rate of 3.25% due 2019, (b) $200,000 principal amount at an annual interest rate of 6.75% due 2020, (c) $300,000 principal amount at an annual interest rate of 6.75% due 2021, (d) $250,000 principal amount at an annual interest rate of 4.75% due 2024, (e) $500,000 principal amount at an annual interest rate of 4.75% due 2028, (f) $350,000 principal amount at an annual interest rate of 5.625% due 2042 and (g) $250,000 principal amount at an annual interest rate of 6.25% due 2046; (3) our $350,000 principal amount unsecured term loan due 2020; (4) our $200,000 principal amount unsecured term loan due 2022; and (5) $734,748 aggregate principal amount of mortgages (excluding premiums, discounts and net debt issuance costs) secured by 13 of our properties (14 buildings) with maturity dates between 2019 and 2043. The 13 mortgaged properties (14 buildings) had a carrying value (before accumulated depreciation) of $1,034,799 at December 31, 2018. We also had two properties subject to capital leases with lease obligations totaling $9,832 at December 31, 2018; these two properties had a carrying value (before accumulated depreciation) of $34,568 at December 31, 2018, and the capital leases expire in 2026.

We have a $1,000,000 revolving credit facility that is available for general business purposes, including acquisitions. The maturity date of our revolving credit facility is January 15, 2022, and, subject to the payment of an extension fee and meeting other conditions, we have the option to extend the maturity date of the facility for an additional year. Our revolving credit facility provides that we can borrow, repay and re-borrow funds available under our revolving credit facility until maturity, and no principal repayment is due until maturity. Our revolving credit facility requires annual interest to be paid on borrowings at the rate of LIBOR plus a premium of 120 basis points per annum, and a facility fee of 25 basis points per annum on the total amount of lending commitments under the facility. The interest rate premium and facility fee are each subject to adjustment based upon changes to our credit ratings. The facility also includes a feature pursuant to which in certain circumstances maximum borrowings under the facility may be increased to up to $2,000,000.

As of December 31, 2018, the annual interest rate payable on borrowings under our revolving credit facility was 3.6%. The weighted average annual interest rates for borrowings under our revolving credit facility were 3.0%, 2.4% and 1.8% for the years ended December 31, 2018, 2017 and 2016, respectively. As of December 31, 2018, we had $139,000 outstanding and $861,000 available for borrowing, and as of February 27, 2019, we had $238,000 outstanding and $762,000 available for borrowing under our revolving credit facility. We incurred interest expense and other associated costs related to our revolving credit facility of $10,348, $14,346 and $13,100 for the years ended December 31, 2018, 2017 and 2016, respectively.

We have a $350,000 term loan that matures in January 2020 and is prepayable without penalty at any time. This term loan requires annual interest to be paid at the rate of LIBOR plus a premium of 140 basis points that is subject to adjustment based upon changes to our credit ratings. At December 31, 2018, the annual interest rate payable on amounts outstanding under this term loan was 3.7%. The weighted average annual interest rate for amounts outstanding under this term loan was 3.4%, 2.5% and 1.9% for the years ended December 31, 2018, 2017 and 2016, respectively. We incurred interest expense and other associated costs related to this term loan of $12,555, $9,338 and $7,231 for the years ended December 31, 2018, 2017 and 2016, respectively. This term loan includes an accordion feature under which maximum borrowings may be increased to up to $700,000 in certain circumstances.

We also have a $200,000 term loan that matures in September 2022 and is prepayable without penalty at any time. This term loan requires annual interest to be paid at the rate of LIBOR plus a premium of 135 basis points that is subject to adjustment based upon changes to our credit ratings. At December 31, 2018, the annual interest rate payable on amounts outstanding under this term loan was 3.9%. The weighted average annual interest rate for amounts outstanding under this term loan was 3.4%, 2.7% and 2.3% and for the years ended December 31, 2018, 2017 and 2016, respectively. We incurred interest expense and other associated costs related to this term loan of $7,095, $5,756 and $4,889 for the years ended December 31, 2018, 2017 and 2016, respectively. This term loan includes an accordion feature under which maximum borrowings may be increased to up to $400,000 in certain circumstances.

Our revolving credit facility and term loan agreements and our senior unsecured notes indentures and their supplements provide for acceleration of payment of all amounts due thereunder upon the occurrence and continuation of certain events of default, such as, in the case of our revolving credit facility and term loan agreements, a change of control of us, as defined, which includes RMR LLC ceasing to act as our business and property manager. Our revolving credit facility and term loan agreements and our senior unsecured notes indentures and their supplements also contain a number of covenants, including covenants that restrict our ability to incur debts, and generally require us to maintain certain financial ratios, and our revolving credit facility and term loan agreements restrict our ability to make distributions under certain circumstances. We believe we were in compliance with the terms and conditions of the respective covenants under our revolving credit facility and term loan agreements and our senior unsecured notes indentures and their supplements at December 31, 2018.

In February 2018, we issued $500,000 of 4.75% senior unsecured notes due 2028. We used the net proceeds of this offering to reduce amounts outstanding under our revolving credit facility.

In February 2016, we issued $250,000 of 6.25% senior unsecured notes due 2046. We used the net proceeds of this offering to repay amounts outstanding under our revolving credit facility and for general business purposes.

In February 2018, in connection with our acquisition of one senior living community, we assumed a $16,748 mortgage note with an annual interest rate of 6.64% and a maturity date in June 2023.

In March 2018, in connection with our acquisition of one MOB (one building), we assumed a $11,050 mortgage note with an annual interest rate of 4.44% and a maturity date in July 2043.

In June 2018, in connection with our acquisition of two senior living communities, we assumed a $16,588 mortgage note with an annual interest rate of 5.75% and a maturity date in October 2022.

In July 2016, we entered loan agreements and obtained an aggregate $620,000 secured debt financing that matures in August 2026. These loans are secured by one MOB (two buildings) located in Massachusetts and require interest to be paid at a weighted average fixed annual interest rate of 3.53%. We used the net proceeds from these loans to repay, in part, the then outstanding amount under our revolving credit facility and for general business purposes. The loan agreements contain customary covenants and provide for acceleration of payment of all amounts due thereunder upon the occurrence and continuation of certain events of default. The property encumbered by these mortgages is owned by a joint venture in which we own a 55% equity interest.

In January 2018, we prepaid, at par plus accrued interest, a mortgage note secured by one of our properties with an outstanding principal balance of approximately $4,338, a maturity date in September 2043 and an annual interest rate of 4.4%. In July 2018, we prepaid, at par plus accrued interest, mortgage notes secured by 12 of our properties with an aggregate outstanding principal balance of approximately $90,602, maturity dates in October 2018 and a weighted average annual interest rate of 5.0%. In September 2018, we prepaid, at par plus accrued interest, a mortgage note secured by one of our properties with an outstanding principal balance of approximately $6,325, a maturity date in January 2019 and an annual interest rate of 4.7%. As a result of these prepayments, we recorded a loss on early extinguishment of debt of $22 for the year ended December 31, 2018. We prepaid these mortgages using cash on hand and borrowings under our revolving credit facility.

In April 2017, we prepaid, at par plus accrued interest, a mortgage note secured by 17 of our properties with an outstanding principal balance of approximately $277,837 plus an aggregate premium of $5,449, a maturity date in September 2019 and an annual interest rate of 6.71%. In May 2017, we prepaid, at par plus accrued interest, a mortgage note secured by one of our properties with an outstanding principal balance of approximately $10,579, a maturity date in August 2017 and an annual interest rate of 6.15%. In June 2017, we prepaid, at par plus accrued interest, a mortgage note secured by one of our properties with an outstanding principal balance of approximately $8,807, a maturity date in August 2037 and an annual interest rate of 5.95%. In December 2017, we prepaid, at par plus accrued interest, a mortgage note secured by one of our properties with an outstanding principal balance of approximately $8,403, a maturity date in April 2018 and an annual interest rate of 6.73%. As a result of these prepayments, we recorded a loss on early extinguishment of debt of $7,627 for the year ended December 31, 2017. We prepaid these mortgages using cash on hand and borrowings under our revolving credit facility.

In January 2016, we prepaid, at par plus accrued interest, a mortgage note secured by one of our properties with an outstanding principal balance of approximately $6,115, a maturity date in April 2016 and an annual interest rate of 5.97%. In April 2016, we prepaid, at par plus accrued interest, a mortgage note secured by one of our properties with an outstanding principal balance of approximately $18,000, a maturity date in July 2016 and an annual interest rate of 4.65%. In July 2016, we prepaid, at par plus accrued interest, a mortgage note secured by one of our properties with an outstanding principal balance of approximately $11,871, a maturity date in November 2016 and an annual interest rate of 6.25%. In September 2016, we prepaid, at par plus accrued interest, mortgage notes secured by two of our properties with an outstanding principal balance of approximately $79,957, maturity dates in November 2016 and a weighted average annual interest rate of 5.92%. In October 2016, we prepaid, at par plus prepayment premiums and accrued interest, mortgage notes secured by eight properties with an aggregate principal balance of $42,542, maturity dates in May 2017 and a weighted average annual interest rate of 6.54%. In December 2016, we prepaid, at par plus accrued interest, a mortgage note secured by one of our properties with an outstanding principal balance of approximately $5,428, a maturity date in March 2017 and an annual interest rate of 5.86%. As a result of these prepayments, we recognized a net loss on early extinguishment of debt of $526 for the year ended December 31, 2016. We prepaid these mortgages using cash on hand and borrowings under our revolving credit facility.

At December 31, 2018 and 2017, our outstanding senior unsecured notes and secured debt consisted of the following:



				December 31, 2018				December 31, 2017
Senior Unsecured Notes	Coupon		Maturity	Face Amount		Unamortized Discount		Face Amount		Unamortized Discount
Senior unsecured notes	3.250	%	May 19	$	400,000	$	19	$	400,000	$	78
Senior unsecured notes	6.750	%	Apr 20	200,000		274		200,000		488
Senior unsecured notes	6.750	%	Dec 21	300,000		1,558		300,000		2,093
Senior unsecured notes	4.750	%	May 24	250,000		421		250,000		500
Senior unsecured notes	4.750	%	Feb 28	500,000		7,702		—		—
Senior unsecured notes	5.625	%	Aug 42	350,000		—		350,000		—
Senior unsecured notes	6.250	%	Feb 46	250,000		—		250,000		—
Total senior unsecured notes				$	2,250,000	$	9,974	$	1,750,000	$	3,159



	Principal Balance as of December 31,							Number of Properties as Collateral	Net Book Value of Collateral as of December 31,
	Principal Balance as of December 31,							Number of Properties as Collateral	Net Book Value of Collateral as of December 31,
Secured and Other Debt	2018⁽¹⁾		2017⁽¹⁾		Interest Rate		Maturity	At December 31, 2018	2018		2017
Mortgage notes ⁽²⁾	$	—	$	12,552	6.31	%	Oct 18	—	$	—	$	16,470
Mortgage notes ⁽²⁾	—		11,858		6.24	%	Oct 18	—	—		15,025
Mortgage note ⁽²⁾	—		67,749		4.47	%	Oct 18	—	—		175,975
Mortgage note ⁽²⁾	—		6,430		4.69	%	Jan 19	—	—		9,477
Mortgage note	42,618		43,558		3.79	%	Jul 19	4	61,199		62,596
Mortgage note	2,037		2,603		7.49	%	Jan 22	1	14,602		15,099
Mortgage note	13,146		13,741		6.28	%	Jul 22	1	24,064		24,414
Mortgage note	11,180		11,392		4.85	%	Oct 22	1	20,602		21,065
Mortgage note	16,441		—		5.75	%	Oct 22	2	20,342		—
Mortgage note	16,442		—		6.64	%	Jun 23	1	20,538		—
Mortgage notes ⁽³⁾	620,000		620,000		3.53	%	Aug 26	1	745,079		764,622
Mortgage note	1,983		2,395		6.25	%	Feb 33	1	4,402		4,473
Mortgage note	10,901		—		4.44	%	Jul 43	1	13,816		—
Mortgage note ⁽²⁾	—		4,338		4.38	%	Sep 43	—	—		7,290
Capital Leases	9,832		10,694		7.70	%	Apr 26	2	17,970		18,525
Total secured	$	744,580	$	807,310				15	$	942,614	$	1,135,031


(1)	The principal balances are the amounts stated in the contracts. In accordance with GAAP, our carrying values and recorded interest expense may be different because of market conditions at the time we assumed certain of these debts. As of December 31, 2018 and 2017, the unamortized net premiums and debt issuance costs on certain of these mortgages were $394 and $1,906, respectively.


(2)	In 2018, we prepaid these debts.


(3)	In July 2016, we entered loan agreements and obtained an aggregate $620,000 secured debt financing that matures in August 2026. These loans are secured by one MOB (two buildings). The property encumbered by these mortgages is owned by a joint venture in which we own a 55% equity interest.

Interest on our senior unsecured notes are payable either semi-annually or quarterly in arrears; however, no principal repayments are due until maturity. Required monthly payments on our mortgages include principal and interest. Payments under our capital leases are due monthly. We include amortization of capital lease assets in depreciation and amortization expense.

Required principal payments on our outstanding debt as of December 31, 2018, are as follows:



Year	Principal Payment
2019	$	446,140
2020	553,785
2021	304,083
2022	378,357
2023	16,657
Thereafter	1,984,558		⁽¹⁾

	$	3,683,580

(1) The carrying value of our total debt outstanding as of December 31, 2018, including unamortized debt issuance costs, premiums and discounts was $3,648,417.