6. LONG-TERM DEBT AND LEASE OBLIGATIONS

Long-term debt, net consists of the following:



	December 31,
	2018		2017
	(in millions)
Revolving credit facility	$	—	$	—
Term Loan A Facility	83.8		92.5
Term Loan B Facility	1,511.2		1,526.8
7.75% Notes due 2019	100.0		200.0
6.625% Notes due 2022	450.0		550.0
6.50% Notes due 2027	500.0		500.0
6.25% Notes due 2026	400.0		—
6.25% Notes due 2025	700.0		700.0
6.25% Notes due 2021	—		400.0
Foreign credit facilities	127.1		53.2
Capital lease obligations	3.4		28.3
Debt	3,875.5		4,050.8
Less: Current portion of long-term debt	121.6		5.9
Long-term debt	3,753.9		4,044.9
Less: Debt issuance costs	67.1		75.6
Long-term debt, net	$	3,686.8	$	3,969.3

SENIOR SECURED CREDIT FACILITIES In 2017, Holdings and American Axle & Manufacturing, Inc. (AAM Inc.) entered into a credit agreement (the Credit Agreement). In connection with the Credit Agreement, Holdings, AAM, Inc. and certain of their restricted subsidiaries entered into a Collateral Agreement and Guarantee Agreement with the financial institutions party thereto as collateral agent and administrative agent. The Credit Agreement includes a $100.0 million term loan A facility (the Term Loan A Facility), a $1.55 billion term loan B facility (the Term Loan B Facility) and a $932 million multi-currency revolving credit facility (the Revolving Credit Facility, and together with the Term Loan A Facility and the Term Loan B Facility, the Senior Secured Credit Facilities). The proceeds of the Revolving Credit Facility are used for general corporate purposes. We incurred debt issuance costs of $54.0 million in 2017 related to the Senior Secured Credit Facilities.

As of December 31, 2018, we have prepaid $8.8 million of the outstanding principal on our Term Loan A Facility and $15.5 million of the outstanding principal on our Term Loan B Facility. These payments satisfy our obligation for principal payments under the Term Loan A Facility and Term Loan B Facility for the next four quarters. As a result, there are no amounts related to the Term Loan A Facility or Term Loan B Facility in the Current portion of long-term debt line item in our Consolidated Balance Sheet as of December 31, 2018.

At December 31, 2018, $894.7 million was available under the Revolving Credit Facility. This availability reflects a reduction of $37.3 million for standby letters of credit issued against the facility.

The Senior Secured Credit Facilities provide back-up liquidity for our foreign credit facilities. We intend to use the availability of long-term financing under the Senior Secured Credit Facilities to refinance any current maturities related to such debt agreements that are not otherwise refinanced on a long-term basis in their local markets, except where otherwise reclassified to Current portion of long-term debt on our Consolidated Balance Sheet.

6.25% NOTES DUE 2026 In the first quarter of 2018, we issued $400.0 million in aggregate principal amount of 6.25% senior notes due 2026 (the 6.25% Notes due 2026). Proceeds from the 6.25% Notes due 2026 were used primarily to fund the tender offer for the 6.25% senior notes due 2021 (the 6.25% Notes due 2021) described below. We paid debt issuance costs of $6.6 million during 2018 related to the 6.25% Notes due 2026.

TENDER OFFER OF 6.25% NOTES DUE 2021 Also during the first quarter of 2018, we made a tender offer for our 6.25% Notes due 2021. Under this tender offer, we retired the $400.0 million of the 6.25% Notes due 2021 and expensed $2.5 million for the write-off of the remaining unamortized debt issuance costs that we had been amortizing over the expected life of the borrowing and $8.0 million in tender premiums.

REDEMPTION OF 6.625% NOTES DUE 2022 In the second quarter of 2018, we voluntarily redeemed a portion of our 6.625% Notes due 2022. This resulted in a principal payment of $100.0 million, and a payment of $0.8 million in accrued interest. During 2018, we expensed $0.8 million for the write-off of a portion of the remaining unamortized debt issuance costs that we had been amortizing over the expected life of the borrowing and $3.3 million for an early redemption premium.

REDEMPTION OF 7.75% NOTES DUE 2019 In the fourth quarter of 2018, we voluntarily redeemed a portion of our 7.75% Notes due 2019. This resulted in a principal payment of $100.0 million and $3.9 million in accrued interest. We also expensed approximately $0.3 million for the write-off of a portion of the unamortized debt issuance costs that we had been amortizing over the expected life of the borrowing, and approximately $4.5 million for an early redemption premium.

6.50% NOTES DUE 2027 AND 6.25% NOTES DUE 2025 During the first quarter of 2017, we issued $700.0 million in aggregate principal amount of 6.25% senior notes due 2025 and $500.0 million in aggregate principal amount of 6.50% senior notes due 2027 (the Notes). Proceeds from the Notes were used primarily to fund the cash consideration related to our acquisition of MPG, related fees and expenses, refinance certain existing indebtedness of MPG and borrowings under our previous revolving credit facility, which has been replaced by our new Revolving Credit Facility, together with borrowings under the Senior Secured Credit Facilities. We incurred debt issuance costs of $37.2 million in 2017 related to the Notes.

REPAYMENT OF MPG INDEBTEDNESS Upon our acquisition of MPG in 2017, we assumed approximately $1.9 billion of existing MPG indebtedness, which we repaid in its entirety on the date of acquisition. This indebtedness was comprised of approximately $0.2 billion of a Euro denominated term loan, approximately $1.0 billion of a U.S. dollar denominated term loan and approximately $0.7 billion of outstanding MPG bonds. Upon settlement of the debt, we paid approximately $24.6 million of accrued interest. In addition, we expensed $2.7 million of prepayment premiums related to the extinguishment of MPG's debt, which has been presented in the Debt refinancing and redemption costs line item within our Consolidated Statements of Operations for the year ended December 31, 2017.

LEASES We lease certain facilities and furniture under capital leases expiring at various dates. The gross asset cost of our capital leases was $10.5 million and $10.1 million at December 31, 2018 and 2017, respectively. The net book value included in property, plant and equipment, net on the balance sheet was $3.4 million and $5.3 million at December 31, 2018 and 2017, respectively. The weighted-average interest rate on these capital lease obligations at December 31, 2018 was 7.9%.

In the second quarter of 2018, we reached a settlement agreement related to a capital lease obligation that we had recognized as part of the acquisition of MPG, and as a result we recorded a gain of $15.6 million, which is recorded in the Gain on settlement of capital lease line item of the Consolidated Statements of Operations. During 2018, we paid $11.4 million related to this settlement agreement.

We also lease certain manufacturing machinery and equipment, commercial office and production facilities, vehicles and other assets under operating leases expiring at various dates. Future minimum payments under non-cancelable operating leases are as follows: $32.6 million in 2019, $24.3 million in 2020, $16.2 million in 2021, $12.6 million in 2022, and $7.5 million in 2023. Our total expense relating to operating leases was $36.9 million, $28.6 million and $26.9 million in 2018, 2017 and 2016, respectively.

FOREIGN CREDIT FACILITIES We utilize local currency credit facilities to finance the operations of certain foreign subsidiaries. These credit facilities, some of which are guaranteed by Holdings and/or AAM, Inc., expire at various dates through January 2021. At December 31, 2018, $127.1 million was outstanding under these facilities and an additional $78.2 million was available. At December 31, 2017, $53.2 million was outstanding under these facilities and an additional $159.7 million was available.

DEBT MATURITIES Aggregate maturities of long-term debt are as follows (in millions):



2019	$	152.2
2020	37.0
2021	91.5
2022	530.0
2023	15.5
Thereafter	3,049.3
Total	$	3,875.5

INTEREST EXPENSE AND INVESTMENT INCOME Interest expense was $216.3 million in 2018, $195.6 million in 2017 and $93.4 million in 2016. The change in interest expense in 2018, as compared to 2017, is primarily attributable to additional interest expense incurred on borrowings outstanding under our Senior Secured Credit Facilities entered into in April 2017, as well as on $700.0 million aggregate principal amount of 6.25% senior notes due 2025 and $500.0 million in aggregate principal amount of 6.50% senior notes due 2027, which were issued in March 2017. The change in interest expense in 2017, as compared to 2016, primarily reflects the interest incurred on these additional borrowings in 2017.

We capitalized interest of $28.4 million in 2018, $18.3 million in 2017 and $6.5 million in 2016. The weighted-average interest rate of our long-term debt outstanding at December 31, 2018 was 5.9% as compared to 5.7% and 6.6% at December 31, 2017 and 2016, respectively.

Investment income was $2.0 million in 2018 and $2.9 million in 2017 and 2016. Investment income includes interest earned on cash and cash equivalents and realized and unrealized gains and losses on our short-term investments during the period.