Long-Term Debt and Credit Facility (Tables)

3 Months Ended

Mar. 31, 2015

Debt Disclosure [Abstract]

Principal amount, carrying amount, and interest expense of the notes

The following tables provide additional information regarding the Convertible Notes (in millions of dollars):

	March 31, 2015		December 31, 2014
Principal amount	$	175.0	$	175.0
Less: unamortized issuance discount	—		(2.5		)
Carrying amount, net of discount	$	175.0	$	172.5

	Quarter Ended March 31,
	2015		2014
Contractual coupon interest	$	2.0	$	2.0
Amortization of discount	2.4		2.1
Amortization of deferred financing costs	0.3		0.3
Total interest expense1	$	4.7	$	4.4

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¹  A portion of the interest relating to the Convertible Notes was capitalized as construction in progress.