7. Notes Payable

The following is a summary of our indebtedness:



	Balance at
(in millions)	March 31, 2013		December 31, 2012
Senior unsecured notes
5.45% Notes, due 2013	$	199.9	$	199.9
5.08% Notes, due 2015	249.6		249.5
5.75% Notes, due 2017	246.4		246.3
4.70% Notes, due 2021	248.7		248.7
3.07% Notes, due 2022	346.4		346.3
5.00% Notes, due 2023	247.5		247.5
	1,538.5		1,538.2
Secured notes
1.02% – 6.00% Conventional Mortgage Notes, due 2014 – 2045	907.7		934.6
Tax-exempt Mortgage Note due 2028 (1.35% floating rate)	37.4		37.7
	945.1		972.3
Total notes payable	$	2,483.6	$	2,510.5

Floating rate debt included in secured notes (1.02%)	$	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 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 March 31, 2013, we had no balances outstanding on our $500 million unsecured line of credit. However, we had outstanding letters of credit totaling approximately $11.6 million, leaving approximately $488.4 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.

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 March 31, 2013 and 2012, the weighted average interest rate on our floating rate debt was approximately 1.1%.

Our indebtedness had a weighted average maturity of 6.8 years at March 31, 2013. Scheduled repayments on outstanding debt, including our line of credit and scheduled principal amortizations, and the weighted average interest rate on maturing debt at March 31, 2013 were as follows:



(in millions)	Amount		Weighted Average Interest Rate
2013	$	202.4	5.4	%
2014	35.4		3.2
2015	252.0		5.1
2016 (1)	2.2		—
2017	249.2		5.7
Thereafter	1,742.4		4.2
Total	$	2,483.6	4.5	%

(1) Includes only scheduled principal amortizations.