Long-Term Debt and Credit Facility (Tables)

9 Months Ended

Sep. 30, 2015

Debt Disclosure [Abstract]

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

The following table provides additional information regarding the Convertible Notes (in millions of dollars):

	Quarter Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Contractual coupon interest	$	—	$	2.0	$	2.0	$	5.9
Amortization of discount	—		2.3		2.4		6.7
Amortization of deferred financing costs	—		0.3		0.3		0.9
Total interest expense1	$	—	$	4.6	$	4.7	$	13.5

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