text: Interest expense includes the following (in millions):
text: The remaining period over which the unamortized debt discount will be recognized as non-cash interest expense is 7.88 years, 5.88 years, and 17.88 years for the 2017 Senior Convertible Debt, 2015 Senior Convertible Debt and 2017 Junior Convertible Debt, respectively.
text: In November 2017, the Company called for redemption $14.6 million in principal value of the remaining outstanding 2007 Junior Subordinated Convertible Debt (2007 Junior Convertible Debt) with an effective redemption date of December 15, 2017 for which substantially all holders submitted requests to convert. Prior to the call, conversion requests were received in both the second and third quarters of fiscal 2018. Total conversions for fiscal 2018 were for a principal amount of $32.5 million for which the Company settled the principal amount in cash and issued 0.5 million shares of its common stock in respect of the conversion value in excess of the principal amount for the conversions occurring prior to the redemption notice and $41.0  of redemption. A loss on total conversions was recorded for $2.2 million.
text: In June 2017, the Company exchanged, in privately negotiated transactions, $111.3 million aggregate principal amount of its 2007 Junior Convertible Debt for (i) $111.3 million principal amount of 2017 Junior Convertible Debt with a market value of $119.3 million plus (ii) the issuance of 3.2 million shares of the Company's common stock with a value of $254.6 million, of which $56.3 million was allocated to the fair value of the liability and $321.1 million was allocated to the reacquisition of the equity component for total consideration of $374.0 million. The transaction resulted in a loss on settlement of the 2007 Junior Convertible Debt of approximately $13.8 million, which represented the difference between the fair value of the liability component at time of repurchase and the sum of the carrying values of the debt component and any unamortized debt issuance costs. The debt discount on the new 2017 Junior Convertible Debt was the difference between the par value and the fair value of the debt resulting in a debt discount of $55.1 million which will be amortized to interest expense using the effective interest method over the term of the debt.
text: In February 2017, the Company issued the 2017 Senior Convertible Debt and 2017 Junior Convertible Debt for net proceeds of $2.04 billion and $567.7 million, respectively. In connection with the issuance of these instruments, the Company incurred issuance costs of $33.7 million, of which $17.8 million and $3.4 million was recorded as convertible debt issuance costs related to the 2017 Senior Convertible Debt and 2017 Junior Convertible Debt, respectively, and will be amortized using the effective interest method over the term of the debt. The balance of $12.5 million in fees was recorded to equity. Interest on both instruments is payable semi-annually on February 15 and August 15 of each year.
text: In February 2015, the Company issued the 2015 Senior Convertible Debt for net proceeds of approximately $1.69 billion. In connection with the issuance, the Company incurred issuance costs of $30.3 million, of which $20.4 million was recorded as debt issuance costs and will be amortized using the effective interest method over the term of the debt. The balance of $9.9 million was recorded to equity.
text: The Company utilized the proceeds from the issuances of the 2017 Senior Convertible Debt, 2017 Junior Convertible Debt, and 2015 Senior Convertible Debt to reduce amounts borrowed under its Credit Facility and to settle a portion of the 2007 Junior Convertible Debt in privately negotiated transactions. In February 2017 and February 2015, the Company settled $431.3 million and $575.0 million, respectively, in aggregate principal of its 2007 Junior Convertible Debt. The February 2015 repurchase consisted solely of cash. In February 2017, the Company used cash of $431.3 million and an aggregate of 12.0 million in shares of the Company's common stock valued at $862.7 million for total consideration of $1.29 billion to repurchase $431.3 million of the 2007 Junior Convertible Debt, of which $188.0 million was allocated to the liability component and $1.11 billion was allocated to the equity component. In addition, in February 2017, there was an inducement fee of $5.0 million which was recorded in the consolidated statements of income in loss on settlement of debt. The consideration transferred in February 2015 was $1.13 billion, of which $238.3 million was allocated to the liability component and $896.3 million was allocated to the equity component. In the case of both settlements of the 2007 Junior Convertible Debt, the consideration was allocated to the liability and equity components using the equivalent rate that reflected the borrowing rate for a similar nonconvertible debt prior to the retirement. The transactions resulted in a loss on settlement of debt of approximately $43.9 million and $50.6 million in fiscal 2017 and fiscal 2015, respectively, which represented, in each case, the difference between the fair value of the liability component at time of repurchase and the sum of the carrying values of the debt component and any unamortized debt issuance costs.

Table:
Year Ended March 31,
2019
2018
2017
Debt issuance amortization
$12.9
$3.1
$2.4
Debt discount amortization
2.2
—
—
Interest expense
291.8
6.6
40.4
Total interest expense on Senior Secured Indebtedness
306.9
9.7
42.8
Debt issuance amortization
3.6
3.5
2.1
Debt discount amortization
112.4
106.1
56.1
Coupon interest expense
77.1
77.3
44.5
Total interest expense on Convertible Debt
193.1
186.9
102.7
Other interest expense
2.9
2.4
0.8
Total interest expense
$502.9
$199.0
$146.3

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