Borrowings (net of debt issuance costs, debt discount, and amortization) consist of the following:



(in millions)	June 30, 2018		December 31, 2017
3.25% convertible senior notes	$	145.4	$	141.9
Revolving credit facility	50.7		50.7
Total	196.1		192.6
Less current maturities ⁽¹⁾	—		—
Total long-term debt	$	196.1	$	192.6

⁽¹⁾ There are no required principal payments due under the 3.25% convertible senior notes or the revolving credit facility until maturities in November 2021 and October 2022, respectively.

Total debt principal payments over the next five years are as follows:



(in millions)	Q3-Q4 2018		2019		2020		2021		2022
Debt principal payments	$	—	$	—	$	—	$	172.5	$	50.7

3.25% Convertible Senior Notes Due November 1, 2021

In May 2016, the Company issued $172.5 million aggregate principal amount of 3.25% convertible senior notes due November 1, 2021 ("the Notes"), unless earlier repurchased by the Company or converted pursuant to their terms. Interest is payable semiannually in arrears on May 1 and November 1 each year and commenced on November 1, 2016.

The Notes are governed by an Indenture (the "Indenture") between the Company, as issuer, and U.S. Bank National Association as trustee. Upon conversion, the Company will pay or deliver cash, shares of the Company's common stock, or a combination of cash and shares of common stock, at the Company's election. The initial conversion rate is 54.2741 shares of common stock per $1,000 principal amount of Notes. The initial conversion price is $18.4250 per share of common stock. The conversion rate will be subject to adjustment upon the occurrence of certain specified events but will not be adjusted for accrued and unpaid interest. In addition, upon the occurrence of a make-whole fundamental change (as defined in the Indenture), the Company may be required, in certain circumstances, to increase the conversion rate by a number of additional shares for a holder that elects to convert its Notes in connection with such make-whole fundamental change.

Prior to the close of business on the business day immediately preceding August 1, 2021, the Notes will be convertible only under the following circumstances:



=	during any calendar quarter and only during such calendar quarters, if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day;
=	during the five business day period after any 10 consecutive trading day period (the “measurement period”) in which the trading price per $1,000 principal amount of Notes was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day; or
=	upon the occurrence of specified corporate events.

On or after August 1, 2021 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert all or any portion of their Notes, in multiples of $1,000 principal amount, at the option of the holder regardless of the foregoing circumstances. As of June 30, 2018, no event has occurred that would permit the conversion of the Notes. The Notes are the Company’s senior unsecured obligations.

In accounting for the issuance of the Notes, the Company separated the Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of a similar liability that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was determined by deducting the fair value of the liability component from the face value of the Notes as a whole. The excess of the principal amount of the liability component over its carrying amount is amortized to interest expense over the term of the Notes. The equity component is not remeasured as long as it continues to meet the conditions for equity classification.

In accounting for the transaction costs related to the Notes issuance, the Company allocated the total amount incurred to the liability and equity components based on their relative values. Issuance costs attributable to the liability component, totaling $5.0 million, are being amortized to interest expense over the term of the Notes, and issuance costs attributable to the equity component, totaling $1.3 million, were netted with the equity component in stockholders' equity. Additionally, the Company recorded a deferred tax asset of $0.5 million on a portion of the equity component transaction costs which are deductible for tax purposes and immediately recorded a valuation allowance against this deferred tax asset.

The Notes consist of the following:



(in millions)	June 30, 2018			December 31, 2017
Liability component:
Principal	$	172.5		$	172.5
Less debt issuance costs and debt discount, net of amortization	(27.1		)	(30.6		)
Total	145.4			141.9
Less current maturities ⁽¹⁾	—			—
Long-term portion	$	145.4		$	141.9

Equity component ⁽²⁾	$	29.9		$	29.9

⁽¹⁾ There are no required principal payments due until maturity in November 2021.

⁽²⁾ Recorded in the Consolidated Balance Sheets within additional paid-in capital, inclusive of the $1.3 million of issuance costs in equity.

The total estimated fair value of the Notes at June 30, 2018 was $193.7 million. The fair value was determined based on the closing trading price of the Notes as of the last trading day for the second quarter of 2018.

The following table sets forth total interest expense recognized related to the Notes:



	Three Months Ended June 30,				Six Months Ended June 30,
(in millions)	2018		2017		2018		2017
3.25% coupon	$	1.4	$	1.4	$	2.8	$	2.8
Amortization of debt issuance costs	0.2		0.2		0.4		0.4
Amortization of debt discount	1.6		1.5		3.1		2.9
Total	$	3.2	$	3.1	$	6.3	$	6.1

Note Hedges

To minimize the impact of potential economic dilution upon conversion of the Notes, the Company entered into convertible note hedge transactions (the “Note Hedges”) with respect to its common stock. In the second quarter of 2016, the Company paid an aggregate amount of $44.5 million for the Note Hedges. The Note Hedges will expire upon maturity of the Notes. The Note Hedges are intended to offset the potential dilution upon conversion of the Notes and/or offset any cash payments the Company is required to make in excess of the principal amount upon conversion of the Notes in the event that the market value per share of the Company's common stock, as measured under the Note Hedges, is greater than the strike price of the Note Hedges, which initially corresponds to the initial conversion price of the Notes and is subject to anti-dilution adjustments substantially similar to those applicable to the conversion rate of the Notes. The Note Hedges are separate transactions entered into by the Company, and are not part of the Notes or the Warrants, and have been accounted for as part of additional paid-in capital. Holders of the Notes do not have any rights with respect to the Note Hedges.

Warrants

In addition to the Note Hedges, in the second quarter of 2016, the Company entered into warrant transactions, whereby the Company sold warrants to acquire shares of the Company's common stock at a strike price of $21.1050 per share (the “Warrants”). The Company received aggregate proceeds of $39.1 million from the sale of the Warrants. If the market price per share of the Company's common stock for the reporting period, as measured under the Warrants, exceeds the strike price of the Warrants, the Warrants could have a dilutive effect on the Company's common stock, unless the Company elects, subject to certain conditions, to settle the Warrants in cash. The Warrants are separate transactions entered into by the Company, and are not part of the Notes or the Note Hedges, and have been accounted for as part of additional paid-in capital. Holders of the Notes and Note Hedges do not have any rights with respect to the Warrants.

Revolving Credit Facility

Revolving credit facility borrowings consist of the following:



(in millions)	June 30, 2018		December 31, 2017
$400.0 million revolving credit facility due October 2022	$	50.7	$	50.7
Less current maturities ⁽¹⁾	—		—
Long-term portion	$	50.7	$	50.7

⁽¹⁾ There are no required principal payments due until maturity in October 2022.

On October 11, 2017, the Company entered into a Revolving Credit Facility Agreement (the "New Credit Facility"). The New Credit Facility contains a five-year senior secured revolving credit facility providing for borrowings in an aggregate principal amount at any time outstanding not to exceed $400.0 million. The New Credit Facility serves as refinancing of indebtedness and terminates the Company's Amended and Restated Credit Agreement dated as of January 27, 2014, as amended and restated as of December 31, 2014 and supplemented from time to time (“Prior Credit Facilities”).

The New Credit Facility includes requirements, to be tested quarterly, that the Company maintains (i) a minimum ratio of Consolidated EBITDA to consolidated interest expense of 3.25 to 1.0 (the "Interest Coverage Ratio"), (ii) a maximum ratio of Consolidated total indebtedness to Consolidated EBITDA of 3.75 to 1.0 ("the Leverage Ratio"), and (iii) a maximum ratio of senior secured indebtedness to Consolidated EBITDA of 3.25 to 1.0 (the "Senior Secured Leverage Ratio"). For these ratios, Consolidated EBITDA and consolidated interest expense are calculated using the most recent four consecutive fiscal quarters in a manner defined in the New Credit Facility. At June 30, 2018, the Company was in compliance with these covenants and it expects to remain in compliance with all of its debt covenants over the next twelve months.

The interest rate under the New Credit Facility is variable based on LIBOR at the time of the borrowing and the Company’s leverage as measured by a total indebtedness to Consolidated EBITDA ratio. Based upon the Company’s total indebtedness to Consolidated EBITDA ratio, the Company’s borrowing rate could range from LIBOR + 1.25% to LIBOR + 2.25%. In addition, a commitment fee accrues on the average daily unused portion of the New Credit Facility at a rate of 0.20% to 0.35%.

The weighted-average interest rate on the Company's borrowings under the New Credit Facility and Prior Credit Facilities was 3.49% and 3.67% for the six months ended June 30, 2018 and 2017, respectively. The weighted-average interest rate on the Company's borrowings under the New Credit Facility and Prior Credit Facilities for the six months ended June 30, 2018 and 2017 includes interest expense related to the monthly interest rate swap settlements. The weighted-average commitment fee on the revolving line of credit was 0.25% and 0.39% for the six months ended June 30, 2018 and 2017, respectively.

For supplemental cash flow purposes, cash paid for interest was $4.1 million and $5.8 million for the six months ended June 30, 2018 and 2017, respectively.

See Note 9. Hedging Transactions and Derivative Instruments for information on derivatives used to manage interest rate risk.