10. Notes Payable

The following is a summary of our indebtedness:



	December 31,
(in millions)	2018		2017
Commercial banks
Term loan, due 2022	$	99.6	$	—

Senior unsecured notes (1)
4.78% Notes, due 2021	$	249.1	$	248.7
3.15% Notes, due 2022	347.3		346.6
5.07% Notes, due 2023	248.0		247.6
4.36% Notes, due 2024	248.7		248.5
3.68% Notes, due 2024	247.6		247.2
3.74% Notes, due 2028	396.1		—
	$	1,736.8	$	1,338.6

Total unsecured notes payable	$	1,836.4	$	1,338.6

Secured notes (1)
4.38% – 5.33% Conventional Mortgage Notes, due 2019 – 2045	485.2		866.0
Total notes payable	$	2,321.6	$	2,204.6

Floating rate debt included in unsecured notes (3.34%)	$	99.6	$	—
Floating rate debt included in secured notes (1.92%)	$	—	$	175.0
Value of real estate assets, at cost, subject to secured notes	$	867.9	$	1,534.9


(1)	Unamortized debt discounts and debt issuance costs of $13.9 million and $12.3 million are included in senior unsecured and secured notes payable as of December 31, 2018 and 2017, respectively.

In August 2015, we amended and restated our $500 million unsecured credit facility, which extended the maturity date from September 2015 to August 2019, with two six-month options to extend the maturity date at our election to August 2020, and increased the availability to $600 million, with the option to further increase it to $900 million by either adding additional banks to the facility or obtaining the agreement of the existing banks to increase their commitments. The interest rate on this credit facility is based upon the London Interbank Offered Rate ("LIBOR") plus a margin which is subject to change as our credit ratings change. Advances under this credit facility may be priced at the scheduled rates, or we may enter into bid rate loans with participating banks at rates below the scheduled rates. These bid rate loans have terms of 180 days or less and may not exceed the lesser of $300 million or the remaining amount available under the credit facility. This credit facility is subject to customary financial covenants and limitations. We believe we are in compliance with all such financial covenants and limitations on the date of this filing.

Our credit facility provides us with the ability to issue up to $50 million in letters of credit. While our issuance of letters of credit does not increase our borrowings outstanding under our credit facility, it does reduce the amount available. At December 31, 2018, we had no amounts outstanding on our $600 million credit facility and we had outstanding letters of credit totaling approximately $10.1 million, leaving approximately $589.9 million available under our credit facility.

In May 2018, we extended the term on our $45.0 million unsecured short-term borrowing facility from May 2018 to May 2019. The interest rate is based on LIBOR plus 0.95%. At December 31, 2018, we had no amounts outstanding on this unsecured short-term borrowing facility, leaving $45.0 million available under this facility.

In September 2018, we entered into a $100.0 million three-year unsecured floating-rate term loan with an unrelated third party, which was funded in October 2018. The interest rate on the term loan is based on LIBOR plus a margin which is subject to change as our credit ratings change. See Note 6, "Operating Partnerships" for a further discussion of this transaction.

In October 2018, we repaid at maturity our $175.0 million variable rate secured conventional mortgage notes and $205.0 million of outstanding fixed rate secured conventional mortgage notes which were scheduled to mature in 2018 from our unsecured line of credit, other short-term borrowings, and the $100.0 million term loan discussed above.

Also in October 2018, we issued $400.0 million aggregate principal amount of 4.100% senior unsecured notes due October 15, 2028 (the "2028 Notes") under our existing shelf registration statement. The 2028 Notes were offered to the public at 99.893% of their face amount with a stated rate of 4.100% and a yield to maturity of 4.113%. After giving effect to the settlement of the swap agreements as discussed below in Note 11, "Derivative Financial Instruments and Hedging Activities," and deducting the underwriting discounts and other estimated expenses of the offering, the effective annual interest rate on the 2028 Notes is approximately 3.74%. We received net proceeds of approximately $396.1 million, net of underwriting discounts and other estimated offering expenses. Interest on the 2028 Notes is payable semi-annually on April 15 and October 15, beginning April 15, 2019. We may redeem the 2028 Notes, in whole or in part, at any time at a redemption price equal to the principal amount and accrued interest of the notes being redeemed, plus a make-whole provision. If, however, we redeem the 2028 Notes 90 days or fewer prior to the maturity date, the redemption price will equal 100% of the principal amount of the 2028 Notes to be redeemed plus accrued and unpaid interest on the amount being redeemed to the redemption date. The 2028 Notes are direct, senior unsecured obligations and rank equally with all of our other unsecured and unsubordinated indebtedness. We used the proceeds from the offering of the 2028 Notes to repay outstanding balances on our unsecured line of credit and other short-term borrowings (including amounts incurred to repay the $380.0 million secured unconventional mortgage notes) and the remainder for general corporate purposes.

At December 31, 2018, we had $99.6 million outstanding floating rate debt with a weight average interest rate on this debt of approximately 3.3%. At December 31, 2017, we had outstanding floating rate debt of approximately $175.0 million with a weighted average interest rate on this debt of approximately 1.9%.

Our indebtedness had a weighted average maturity of 4.9 years at December 31, 2018. The table below is a summary of the maturity dates of our outstanding debt and principal amortizations, and the weighted average interest rates on such debt, at December 31, 2018:



(in millions)	Amount			Weighted Average Interest Rate
2019	$	437.3		5.2	%
2020 (1)	(1.9		)	—
2021	248.5			4.8
2022	448.8			3.2
2023	249.8			5.1
Thereafter	939.1			3.9
Total	$	2,321.6		4.2	%


(1)	Includes only amortization of debt discounts and debt issuance costs, net of scheduled principal payments.

Subsequent to December 31, 2018, we repaid $200.0 million of secured notes utilizing our unsecured credit facility.