We have $4,434,107,000 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 $4,464,927,000 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 December 31, 2006, we issued $345,000,000 of 4.75% senior unsecured convertible notes due December 2026, generating net proceeds of $337,517,000. The notes are convertible, in certain circumstances, into cash and, if applicable, shares of common stock at an initial conversion rate of 20.8833 shares per $1,000 principal amount of notes, which represents an initial conversion price of $47.89 per share. In general, upon conversion, the holder of each note would receive, in respect of the conversion value of such note, cash up to the principal amount of such note and common stock for the note's conversion value in excess of such principal amount. In addition, on each of December 1, 2011, December 1, 2016 and December 1, 2021, holders may require us to purchase all or a portion of their notes at a purchase price in cash equal to 100% of the principal amount of the notes to be purchased, plus any accrued and unpaid interest. During the three months ended March 31, 2009, we extinguished $5,000,000 of these notes and recognized a gain of $446,000. During the six months ended June 30, 2010, we extinguished $214,412,000 of these notes, recognized a loss of $8,837,000 and paid $18,552,000 to reacquire the equity component of convertible debt. During the three months ended December 31, 2011, we purchased $3,000 of these notes from holders. As of December 31, 2011, we had $125,585,000 of these notes outstanding.

In July 2007, we issued $400,000,000 of 4.75% senior unsecured convertible notes due July 2027, generating net proceeds of $388,943,000. The notes are convertible, in certain circumstances, into cash and, if applicable, shares of our common stock at an initial conversion rate of 20.0000 shares per $1,000 principal amount of notes, which represents an initial conversion price of $50.00 per share. In general, upon conversion, the holder of each note would receive, in respect of the conversion value of such note, cash up to the principal amount of such note and common stock for the note's conversion value in excess of such principal amount. In addition, on each of July 15, 2012, July 15, 2017 and July 15, 2022, holders may require us to purchase all or a portion of their notes at a purchase price in cash equal to 100% of the principal amount of the notes to be purchased, plus any accrued and unpaid interest. During the three months ended March 31, 2009, we extinguished $5,000,000 of these notes and recognized a gain of $594,000. During the six months ended June 30, 2010, we extinguished $226,914,000 of these notes, recognized a loss of $16,235,000 and paid $21,062,000 to reacquire the equity component of convertible debt. As of December 31, 2011, we had $168,086,000 of these notes outstanding.

During the twelve months ended December 31, 2010, we issued $494,403,000 of 3.00% senior unsecured convertible notes due December 2029, generating net proceeds of $486,084,000. The notes are convertible, in certain circumstances, into cash and, if applicable, shares of common stock at an initial conversion rate of 19.5064 shares per $1,000 principal amount of notes, which represents an initial conversion price of $51.27 per share. In general, upon conversion, the holder of each note would receive, in respect of the conversion value of such note, cash up to the principal amount of such note and common stock for the note's conversion value in excess of such principal amount. In addition, on each of December 1, 2014, December 1, 2019 and December 1, 2024, holders may require us to purchase all or a portion of their notes at a purchase price in cash equal to 100% of the principal amount of the notes to be purchased, plus any accrued and unpaid interest. In connection with this issuance, we recognized $29,925,000 of equity component of convertible debt.

During the year ended December 31, 2009, we extinguished $183,147,000 of senior unsecured notes with a weighted-average interest rate of 7.82% and recognized losses of $19,269,000. During the three months ended June 30, 2010, we issued $450,000,000 of 6.125% senior unsecured notes due 2020 with net proceeds of $446,328,000. During the three months ended September 30, 2010, we issued $450,000,000 of 4.70% senior unsecured notes due 2017 with net proceeds of $445,768,000. During the three months ended December 31, 2010, we issued $450,000,000 of 4.95% senior unsecured notes due 2021 with net proceeds of $443,502,000. 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 $2,112,649,000, collateralized by owned properties, with annual interest rates ranging from 1.22% to 10.00%. The carrying amounts of the secured debt represent the par value of $2,108,384,000 adjusted for any unamortized fair value adjustments. The carrying values of the properties securing the debt totaled $4,048,469,000 at December 31, 2011. During the year ended December 31, 2009, we extinguished 20 secured debt loans totaling $81,715,000 with a weighted-average interest rate of 7.21% and recognized extinguishment losses of $5,838,000. During the year ended December 31, 2010, we issued $157,156,000 of first mortgage loans principal with a rate of 5.45% secured by 15 properties. During the year ended December 31, 2010, we assumed $564,657,000 of first mortgage loans principal with an average rate of 6.06% secured by 60 properties. During the year ended December 31, 2010, we extinguished $194,493,000 of first mortgage loans principal with an average rate of 6.07% and recognized a loss of $9,099,000. During the year ended December 31, 2011, we issued $114,903,000 of first mortgage loans principal with a rate of 5.78% secured by nine properties. During the year ended December 31, 2011, we assumed $940,855,000 of first mortgage loans principal with an average rate of 4.85% secured by 55 properties. During the year ended December 31, 2011, we extinguished $55,317,000 of first mortgage loans principal with an average rate of 5.95% and recognized a gain of $979,000.

We adopted FASB Accounting Standards Codification (“ASC”) topic for Accounting for Convertible Debt Instruments that May Be Settled in Cash upon Conversion (Including Partial Cash Settlement) (“Convertible Debt Guidance”), effective January 1, 2009. It provides guidance on accounting for convertible debt that may be settled in cash upon conversion. It requires bifurcation of the convertible debt instrument into a debt component and an equity component. The value of the debt component is based upon the estimated fair value of a similar debt instrument without the conversion feature. The difference between the contractual principal on the debt and the value allocated to the debt is recorded as an equity component and represents the conversion feature of the instrument. The excess of the contractual principal amount of the debt over its estimated fair value is amortized to interest expense using the effective interest method over the period used to estimate the fair value.

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 December 31, 2011, we were in compliance with all of the covenants under our debt agreements.

At December 31, 2011, the annual principal payments due on these debt obligations are as follows (in thousands):

	Senior		Secured
	Unsecured Notes⁽¹⁾		Debt ⁽¹⁾		Totals
2012	$	76,853	$	122,359	$	199,212
2013		300,000		292,735		592,735
2014		0		203,767		203,767
2015		250,000		184,378		434,378
2016		700,000		190,255		890,255
Thereafter		3,138,074		1,114,890		4,252,964
Totals	$	4,464,927	$	2,108,384	$	6,573,311


(1) Amounts represent principal amounts due and do not include unamortized premiums/discounts or other fair value adjustments as reflected on the balance sheet.