16. Earnings per Share

The following table provides a reconciliation of the numerator and denominator used in computing basic and diluted net loss attributable to common stockholders per common share (in thousands except share amounts):

	Years Ended December 31,
Historical	2017			2016			2015
Numerator:
Net loss attributable to common stockholders	$	(284,002	)	$	(200,042	)	$	(132,118	)


Denominator:
Weighted average common shares outstanding — basic and diluted		153,355,144			134,401,588			109,923,815

Dilutive common stock equivalents would include the dilutive effect of common stock options, convertible debt units, RSUs and warrants for common stock equivalents. Potentially dilutive common stock equivalents were excluded from the diluted earnings per share denominator for all periods because of their anti-dilutive effect. For the year ended 2017 there was 40.9 million potential common shares outstanding as a result of the convertible debt that was excluded from the diluted net loss per share calculation because their effect would have been anti-dilutive.

The table below presents potential shares of common stock that were excluded from the computation as they were anti-dilutive using the treasury stock method (in thousands):

	Year ended December 31,
	2017		2016		2015
Options to purchase common stock		15,181		15,528		11,729
Convertible debt		40,850		40,850		—
Outstanding warrants, convertible to common stock		3,110		3,110		1,350
Unvested restricted stock units		2,575		744		479
Vested restricted stock units, unissued		50		—		—

Total number of potentially issuable shares		61,766		60,232		13,558