We have $4,436,103,000 of senior unsecured notes with annual stated interest rates ranging from 3.00% to 8.00%. The carrying amounts of the senior unsecured notes represent the par value of $4,464,905,000 adjusted for any unamortized premiums or discounts and other basis adjustments related to hedging the debt with derivative instruments. See Note 11 for further discussion regarding derivative instruments. During the three months ended March 31, 2011, we issued $400,000,000 of 3.625% senior unsecured notes due 2016, $600,000,000 of 5.25% senior unsecured notes due 2022 and $400,000,000 of 6.50% senior unsecured notes due 2041, generating net proceeds of $1,381,086,000.

We have secured debt totaling $2,353,856,000, collateralized by owned properties, with annual interest rates ranging from 1.2% to 8.0%. The carrying amounts of the secured debt represent the par value of $2,336,082,000 adjusted for any unamortized fair value adjustments on loan assumptions. The carrying values of the properties securing the debt totaled $4,388,367,000 at March 31, 2012. During the three months ended March 31, 2012, we assumed $158,290,000 of first mortgage loans principal with an average rate of 5.9% secured by seven properties. During the three months ended March 31, 2012, we issued $111,000,000 of first mortgage loans principal with an average rate of 4.2% secured by two properties. During the three months ended March 31, 2012, we extinguished $33,092,000 of first mortgage loans principal with an average rate of 4.3% secured by four properties.

Please see Note 19 regarding senior unsecured note and secured debt activity that occurred subsequent to March 31, 2012.

Our debt agreements contain various covenants, restrictions and events of default. Certain agreements require us to maintain certain financial ratios and minimum net worth and impose certain limits on our ability to incur indebtedness, create liens and make investments or acquisitions. As of March 31, 2012, we were in compliance with all of the covenants under our debt agreements.

At March 31, 2012, the annual principal payments due on these debt obligations were as follows (in thousands):

	Senior		Secured
	Unsecured Notes⁽¹⁾		Debt ⁽¹⁾		Totals
2012	$	202,416⁽²⁾	$	224,279⁽³⁾	$	426,695
2013		300,000		170,693		470,693
2014		0		198,996		198,996
2015		250,000		182,288		432,288
2016		700,000		274,219		974,219
Thereafter		3,012,489		1,285,607		4,298,096
Totals	$	4,464,905	$	2,336,082	$	6,800,987


(1) Amounts represent principal amounts due and do not include unamortized premiums/discounts or other fair value adjustments as reflected on the balance sheet.
(2) $125,563,000 of convertible senior notes were redeemed in April 2012. Please see Note 19 for additional information.
(3) Approximately $185,000,000 of secured debt was extinguished in April 2012. Please see Note 19 for additional information.