9. Debt

Short-Term Debt

The components of short-term debt were as follows:

	December 31,
	2017		2016
	(in millions)
Line of credit	$	39.5	$	51.4

Total short-term debt	$	39.5	$	51.4

As of December 31, 2017 and 2016, we had short-term credit facilities with various financial institutions in an aggregate amount of $905.0 million and $1,005.0 million, respectively. As of December 31, 2017 and 2016, we had $39.5 million and $51.4 million, respectively, of outstanding borrowings, with no assets pledged as support. Our credit facilities include a $600.0 million 5-year facility with PFG, Principal Financial Services, Inc. ("PFS") and Principal Life as co-borrowers that matures March 2022 and a $200.0 million 5-year credit facility, with PFG, PFS, Principal Life and Principal Financial Services V (UK) LTD as co-borrowers, of which $11.0 million matures March 2020 and $189.0 million matures March 2022. The revolving credit facilities are committed and available for general corporate purposes. In addition to the revolving credit facilities, Principal International Chile has the capacity to access up to $60.0 million in unsecured lines of credit offered by Chilean financial institutions and Principal Life has a $45.0 million unsecured line of credit. Our commercial paper programs require 100% back-stop support, of which we had no outstanding balances as of December 31, 2017 and 2016.

The weighted-average interest rate on short-term borrowings as of December 31, 2017 and 2016, was 4.7% and 4.4%, respectively.

Long-Term Debt

The components of long-term debt were as follows:

	December 31, 2017
	Principal		Net unamortized discount, premium and debt issuance costs			Carrying amount
	(in millions)
3.3% notes payable, due 2022	$	300.0	$	(1.9	)	$	298.1
3.125% notes payable, due 2023		300.0		(1.5	)		298.5
3.4% notes payable, due 2025		400.0		(3.5	)		396.5
3.1% notes payable, due 2026		350.0		(3.1	)		346.9
6.05% notes payable, due 2036		505.6		(2.7	)		502.9
4.625% notes payable, due 2042		300.0		(3.3	)		296.7
4.35% notes payable, due 2043		300.0		(3.4	)		296.6
4.3% notes payable, due 2046		300.0		(3.4	)		296.6
4.7% notes payable, due 2055		400.0		(5.0	)		395.0
Non-recourse mortgages and notes payable		49.0		1.6			50.6

Total long-term debt	$	3,204.6	$	(26.2	)	$	3,178.4

	December 31, 2016
	Principal		Net unamortized discount, premium and debt issuance costs			Carrying amount
	(in millions)
3.3% notes payable, due 2022	$	300.0	$	(2.2	)	$	297.8
3.125% notes payable, due 2023		300.0		(1.8	)		298.2
3.4% notes payable, due 2025		400.0		(3.9	)		396.1
3.1% notes payable, due 2026		350.0		(3.3	)		346.7
6.05% notes payable, due 2036		505.6		(2.7	)		502.9
4.625% notes payable, due 2042		300.0		(3.4	)		296.6
4.35% notes payable, due 2043		300.0		(3.4	)		296.6
4.3% notes payable, due 2046		300.0		(3.5	)		296.5
4.7% notes payable, due 2055		400.0		(5.0	)		395.0
Non-recourse mortgages and notes payable (1)		—		(0.7	)		(0.7	)

Total long-term debt	$	3,155.6	$	(29.9	)	$	3,125.7


(1)	Includes external debt issuance costs incurred for long-term affiliated debt issued in a foreign jurisdiction.

Net discount, premium and issuance costs associated with issuing these notes are amortized to expense over the respective terms using the interest method.

On November 10, 2016, we issued $650.0 million of senior notes. We issued a $350.0 million series of notes that bear interest at 3.1% and will mature in 2026 and a $300.0 million series of notes that bear interest at 4.3% and will mature in 2046. Interest on the notes is payable semi-annually on May 15 and November 15 each year, beginning on May 15, 2017. The proceeds from these notes were used to redeem our notes payable due in 2017 and 2019. We incurred a one-time cost to extinguish this debt before the scheduled maturity date.

On May 7, 2015, we issued $400.0 million of senior notes. The notes bear interest at 3.4% and will mature in 2025. Interest on the notes is payable semi-annually on May 15 and November 15 each year, beginning on November 15, 2015. In addition, on May 7, 2015, we issued $400.0 million of junior subordinated notes, which are subordinated to all our senior debt. The notes are callable in 2020 and have a maturity date in 2055. The notes initially bear a fixed rate of interest at 4.7% and convert to a floating rate at the date the notes become callable. Interest on the notes is payable semi-annually on May 15 and November 15 each year. After the call date the notes will bear interest at 3-month LIBOR plus 3.044%, reset quarterly and payable in arrears in February, May, August and November each year. We have the right to defer interest payments on the junior subordinated notes for up to 5 years without resulting in a default, during which time interest will be compounded. The proceeds from these notes were used to redeem our series A and series B preferred stock with the remainder available for general corporate purposes.

On November 16, 2012, we issued $900.0 million of senior notes. We issued a $300.0 million series of notes that bore interest at 1.85% and were to mature in 2017. These notes were repaid following our November 2016 debt issuance. We issued a $300.0 million series of notes that bear interest at 3.125% and will mature in 2023 and a $300.0 million series of notes that bear interest at 4.35% and will mature in 2043. Interest on the notes is payable semi-annually on May 15 and November 15 each year, beginning on May 15, 2013. The proceeds were used to fund our acquisition of Cuprum.

On September 5, 2012, we issued $600.0 million of senior notes. We issued a $300.0 million series of notes that bear interest at 3.3% and will mature in 2022 and a $300.0 million series of notes that bear interest at 4.625% and will mature in 2042. Interest on the notes is payable semi-annually on March 15 and September 15 each year, beginning on March 15, 2013. The proceeds were used for the repayment of the $400.0 million aggregate principal amount of notes due in 2014 and to partially fund our acquisition of Cuprum.

On May 18, 2009, we issued $750.0 million of senior notes. We issued a $400.0 million series of notes that bore interest at 7.875% and were to mature on May 15, 2014. These notes were repaid following our November 2012 debt issuance. We issued a $350.0 million series of notes that bore interest at 8.875% and were to mature on May 15, 2019. These notes were repaid following our November 2016 debt issuance. Interest on the notes was payable semi-annually on May 15 and November 15 each year, beginning on November 15, 2009. The proceeds were primarily used to refinance $440.9 million of notes that matured on August 15, 2009, with the remaining proceeds being used for general corporate purposes.

On October 16 and December 5, 2006, we issued $500.0 million and $100.0 million, respectively, of senior notes. The notes bear interest at a rate of 6.05% per year. Interest on the notes is payable semi-annually on April 15 and October 15 each year and began on April 15, 2007. The notes will mature on October 15, 2036. A portion of the proceeds were used to fund the 2006 acquisition of WM Advisors, Inc., with the remaining proceeds being used for general corporate purposes. A tender offer in the fourth quarter of 2016 resulted in redemption of $94.4 million of the senior notes. We incurred a one-time cost to extinguish this debt before the scheduled maturity date.

The non-recourse mortgages and notes payable are primarily financings for real estate developments. Outstanding principal balances as of December 31, 2017, ranged from $2.8 million to $16.4 million per development with interest rates ranging from 3.9% to 4.8%. Outstanding principal balances as of December 31, 2016, were $0.0 million due to outstanding debt maturing in 2016. Outstanding debt is secured by the underlying real estate properties, which were reported as real estate on our consolidated statements of financial position with a carrying value of $179.6 million and $0.0 million as of December 31, 2017 and 2016, respectively.

As of December 31, 2017, future annual maturities of long-term debt were as follows (in millions):

Year ending December 31:
2018	$	—
2019		—
2020		—
2021		—
2022		298.2
Thereafter		2,880.2

Total future maturities of long-term debt	$	3,178.4