8. Notes Payable

The following is a summary of our indebtedness:



	Balance at
(in millions)	March 31, 2012		December 31, 2011
Commercial Banks
Unsecured line of credit and short-term borrowings	$	—	$	—

Senior unsecured notes
5.93% Notes, due 2012	189.6		189.6
5.45% Notes, due 2013	199.8		199.7
5.08% Notes, due 2015	249.4		249.3
5.75% Notes, due 2017	246.2		246.2
4.70% Notes, due 2021	248.6		248.6
5.00% Notes, due 2023	247.3		247.3
	1,380.9		1,380.7

Total unsecured notes payable	1,380.9		1,380.7

Secured notes
0.89% – 6.00% Conventional Mortgage Notes, due 2012 – 2045	1,011.5		1,012.3
1.32% Tax-exempt Mortgage Note due 2028	38.7		39.1
	1,050.2		1,051.4
Total notes payable	$	2,431.1	$	2,432.1

Floating rate tax-exempt debt included in secured notes (1.32%)	$	38.7	$	39.1
Floating rate debt included in secured notes (0.89% – 1.69%)	206.5		206.4

We have a $500 million unsecured credit facility which matures in September 2015 with an option to extend 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 existing banks 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, all of which we are in compliance.

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, 2012, we had outstanding letters of credit totaling approximately $10.4 million, leaving approximately $489.6 million available under our unsecured line of credit.

At March 31, 2012 and 2011, the weighted average interest rate on our floating rate debt, which includes our unsecured line of credit, was approximately 1.1% and 1.3%, respectively.

Our indebtedness, including our unsecured line of credit, had a weighted average maturity of 6.5 years at March 31, 2012. Scheduled repayments on outstanding debt including all contractual extensions which have been exercised, including our line of credit and scheduled principal amortizations, and the weighted average interest rate on maturing debt at March 31, 2012 were as follows:



(in millions)	Amount		Weighted Average Interest Rate
2012	$	293.2	5.2	%
2013	228.0		5.4	%
2014	11.0		6.0	%
2015	252.4		5.1	%
2016 (1)	2.6		—	%
2017 and thereafter	1,643.9		4.6	%
Total	$	2,431.1	4.8	%

(1) Includes only scheduled principal amortizations.