8. Notes Payable

A. General

Our senior unsecured notes and bonds consist of the following, sorted by maturity date (dollars in millions):

	December 31,			December 31,
	2017			2016
5.375% notes, issued in September 2005 and due in September 2017	$	-		$	175
2.000% notes, issued in October 2012 and due in January 2018	350			350
6.750% notes, issued in September 2007 and due in August 2019	-			550
5.750% notes, issued in June 2010 and due in January 2021	250			250
3.250% notes, $450 issued in October 2012 and $500 issued in December 2017, both due in October 2022	950			450
4.650% notes, issued in July 2013 and due in August 2023	750			750
3.875% notes, issued in June 2014 and due in July 2024	350			350
4.125% notes, $250 issued in September 2014 and $400 issued in March 2017, both due in October 2026	650			250
3.000% notes, issued in October 2016 and due in January 2027	600			600
3.650% notes, issued in December 2017 and due in January 2028	550			-
5.875% bonds, $100 issued in March 2005 and $150 issued in June 2011, both due in March 2035	250			250
4.650% notes, $300 issued in March 2017 and $250 issued in December 2017, both due in March 2047	550			-
Total principal amount	5,250			3,975
Unamortized net original issuance premiums and deferred financing costs	(20		)	(41		)
	$	5,230		$	3,934

The following table summarizes the maturity of our notes and bonds payable as of December 31, 2017, excluding unamortized net original issuance premiums and deferred financing costs (dollars in millions):

Year of Maturity	Principal
2018	$	350	(1)
2019	-
2020	-
2021	250
2022	950
Thereafter	3,700
Totals	$	5,250

(1) In January 2018, we repaid all $350 million of outstanding 2.000% notes, plus accrued and unpaid interest.

As of December 31, 2017, the weighted average interest rate on our notes and bonds payable was 3.9% and the weighted average remaining years until maturity was 9.3 years.

Interest incurred on all of the notes and bonds was $197.1 million for 2017, $171.5 million for 2016 and $179.5 million for 2015. The interest rate on each of these notes and bonds is fixed.

Our outstanding notes and bonds are unsecured; accordingly, we have not pledged any assets as collateral for these or any other obligations. Interest on all of the senior note and bond obligations is paid semiannually.

All of these notes and bonds contain various covenants, including: (i) a limitation on incurrence of any debt which would cause our debt to total adjusted assets ratio to exceed 60%; (ii) a limitation on incurrence of any secured debt which would cause our secured debt to total adjusted assets ratio to exceed 40%; (iii) a limitation on incurrence of any debt which would cause our debt service coverage ratio to be less than 1.5 times; and (iv) the maintenance at all times of total unencumbered assets not less than 150% of our outstanding unsecured debt. At December 31, 2017, we were in compliance with these covenants.

B. Note Issuances

During the three year period ended December 31, 2017 we issued the following notes and bonds (dollars in millions):

2017 Issuances	Date of Issuance	Maturity date		Principal amount issued	Public offering price	Effective yield to maturity
4.125% notes	March 2017	October 2026 (1)	$	400	102.98%	3.75%
4.650% notes	March 2017	March 2047		300	99.97%	4.65%
3.250% notes	December 2017	October 2022 (2)		500	101.77%	2.84%
3.650% notes	December 2017	January 2028		550	99.78%	3.68%
4.650% notes	December 2017	March 2047 (3)		250	105.43%	4.32%

2016 Issuances
3.000% notes	October 2016	January 2027	$	600	98.67%	3.15%

(1) This issuance constitutes a further issuance of, and formed a single series with the senior notes due 2026 issued in September 2014.

(2) This issuance constituted a further issuance of, and formed a single series with the senior notes due 2022 issued in October 2012.

(3) This issuance constituted a further issuance of, and formed a single series with the senior notes due 2047 issued in March 2017.

The net proceeds of $1.3 billion from the December 2017 note offerings were used to redeem all $550.0 million aggregate principal amount of our outstanding 2019 notes, including accrued and unpaid interest, and to repay borrowings outstanding under our $2.0 billion revolving credit facility and, to the extent not used for those purposes, to fund the development and acquisitions of additional properties and for other general corporate purposes. The net proceeds of $705.2 million from the March 2017 note offerings were used to repay borrowings outstanding under our credit facility to fund investment opportunities and for other general corporate purposes.

The net proceeds of approximately $586.7 million from the October 2016 offering were used to repay borrowings outstanding under our credit facility.

C. Note Repayment

In December 2017, we completed the early redemption on all $550.0 million of outstanding 6.75% notes due August 2019, plus accrued and unpaid interest. As a result of the early redemption, we recognized a $42.4 million loss on extinguishment of debt, which represents $0.15 on a diluted per common share basis.

In September 2017, we repaid our $175.0 million of outstanding 5.375% notes, plus accrued and unpaid interest.

In September 2016, we repaid all $275.0 million of outstanding 5.950% notes, plus accrued and unpaid interest.

In November 2015, we repaid $150.0 million of outstanding 5.500% notes, plus accrued and unpaid interest.