7. Notes Payable

The following is a summary of our indebtedness:



	Balance at
(in millions)	September 30, 2013		December 31, 2012
Commercial Banks
Unsecured line of credit and short-term borrowings	$	183.0	$	—

Senior unsecured notes
5.45% Notes, due 2013	200.0		199.9
5.08% Notes, due 2015	249.7		249.5
5.75% Notes, due 2017	246.4		246.3
4.70% Notes, due 2021	248.8		248.7
3.07% Notes, due 2022	346.5		346.3
5.00% Notes, due 2023	247.6		247.5
	1,539.0		1,538.2

Total unsecured notes payable	1,722.0		1,538.2

Secured notes
1.00% – 6.00% Conventional Mortgage Notes, due 2014 – 2045	906.4		934.6
Tax-exempt Mortgage Note due 2028 (1.26% floating rate)	36.6		37.7
	943.0		972.3
Total notes payable	$	2,665.0	$	2,510.5

Other floating rate debt included in secured notes (1.00%)	$	175.0	$	175.0

We have a $500 million unsecured credit facility which matures in September 2015 with an option to extend at our election to September 2016. Additionally, we have the option to increase this credit facility to $750 million by either adding additional banks to the credit facility or obtaining the agreement of the existing banks in the credit facility to increase their commitments. The interest rate is based upon LIBOR plus a margin which is subject to change as our credit ratings change. Advances under the line of credit 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 $250 million or the remaining amount available under the line of credit. The line of credit is subject to customary financial covenants and limitations. We believe we are in compliance with all such financial covenants and limitations.

Our line of credit provides us with the ability to issue up to $100 million in letters of credit. While our issuance of letters of credit does not increase our borrowings outstanding under our line of credit, it does reduce the amount available. At September 30, 2013, we had $170.0 million outstanding on our $500 million unsecured line of credit and we had outstanding letters of credit totaling approximately $11.0 million, leaving approximately $319.0 million available under our unsecured line of credit. As an alternative to our unsecured line of credit, from time to time, we may borrow using an unsecured overnight borrowing facility. Our use of short-term borrowings does not decrease the amount available under our unsecured line of credit. At September 30, 2013, we had $13.0 million short-term borrowings outstanding.

In January 2013, we repaid a 4.95% secured conventional mortgage note which was scheduled to mature on April 1, 2013 for approximately $26.1 million.

At September 30, 2013 and 2012, the weighted average interest rate on our floating rate debt, which includes our unsecured line of credit and short-term borrowings, was approximately 1.0% and 1.1%, respectively.

Our indebtedness, which includes our unsecured line of credit and short-term borrowings, had a weighted average maturity of 6.1 years at September 30, 2013. Scheduled repayments on outstanding debt, including our unsecured line of credit, short-term borrowings and scheduled principal amortizations, and the respective weighted average interest rate on maturing debt at September 30, 2013, were as follows:



(in millions)	Amount		Weighted Average Interest Rate
2013	$	200.8	5.5	%
2014	35.4		3.2
2015	435.0		3.3
2016 (1)	2.2		—
2017	249.2		5.8
Thereafter	1,742.4		4.2
Total	$	2,665.0	4.3	%

(1) Includes only scheduled principal amortizations.