Earnings per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings per Share

Schedule of common stock equivalents excluded in the calculation of diluted income per share

	Year Ended December 31,
	2017		2016		2015
Warrants to purchase common stock		—		—		20,957
Stock options, stock appreciation rights, and ESPP awards		40,009		22,944		25,027

Schedule of computation of basic and diluted net income per share

The following table sets forth the computation of basic and diluted net earnings per share for the years ended December 31, 2017, 2016 and 2015, in thousands of dollars, except share and per share amounts:

	Year Ended December 31,
	2017			2016			2015
Numerator, in thousands:
Net earnings used for calculation of basic EPS	$	57,284		$	91,221		$	13,944
Interest expense on convertible debt		134			543			1,229
Changes in fair value of derivative liabilities		(76	)		(448	)		(589	)
Loss on extinguishment of debt		295			671			2,338
Loss on extinguishment of outstanding debt,
as if converted		(321	)		(1,182	)		(2,494	)
Total adjustments		32			(416	)		484
Net earnings used for calculation of diluted EPS	$	57,316		$	90,805		$	14,428
Denominator:
Weighted average shares outstanding, basic		50,756,603			49,472,434			47,485,258
Effect of dilutive potential common shares:
Shares underlying Convertible Senior Secured Notes		285,257			1,222,363			2,459,009
Shares issuable to settle interest make-whole derivatives		7,012			71,537			804,507
Stock options and stock appreciation rights		2,252,278			942,649			411,606
Total potential dilutive common shares		2,544,547			2,236,549			3,675,122
Weighted average shares outstanding, diluted		53,301,150			51,708,983			51,160,380
Net earings per share, basic	$	1.13		$	1.84		$	0.29
Net earnings per share, diluted	$	1.08		$	1.76		$	0.28