Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Summary of Assumptions used to Value Purchase Rights Granted Under ESPP

The following table summarizes the assumptions used to value the purchase rights granted under the ESPP during the years ended December 31, 2020, 2019 and 2018:

	Year Ended December 31,
	2020			2019			2018
Expected term (years)		0.5			0.5			0.5
Expected volatility		72.0	%		24.0	%		37.0	%
Expected annual dividend		3.9	%		2.1	%		11.3	%
Risk free rate		0.2	%		2.1	%		2.1	%

Restricted Awards

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Schedule of Unvested Restricted Stock Awards

The following table sets forth the number of unvested restricted stock awards and the weighted-average fair value of these awards at the date of grant:

	Restricted Awards			Weighted Average Fair Value at Grant Date		Aggregate Intrinsic Value(1)  ($000s)
Unvested balance December 31, 2019		1,122,085		$	16.09
Granted		996,037		$	10.39
Forfeited		(32,257	)	$	11.18
Vested		(524,450	)	$	16.43
Unvested balance, December 31, 2020		1,561,415		$	12.33	$	18,315

⁽¹⁾

The aggregate intrinsic value is calculated as the market value of our common stock as of December 31, 2020. The market value as of December 31, 2020 was $11.73 per share, which was the closing price of our common stock reported for transactions effected on the NASDAQ Global Select Market on December 31, 2020, the final trading day of 2020.

Performance Awards

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Schedule of Unvested Performance-based Restricted Stock Units Awards

The following table sets forth the number of unvested PSUs and the weighted-average fair value of these awards at the date of grant:

	Performance Awards			Weighted Average Fair Value at Grant Date		Aggregate Intrinsic Value(1)  ($000s)
Unvested balance December 31, 2019		517,061		$	21.72
Granted		322,209		$	15.45
Forfeited		(132,700	)	$	28.20
Vested		—		$	—
Unvested balance, December 31, 2020		706,570		$	17.64	$	8,288

⁽¹⁾ The aggregate intrinsic value is calculated as the market value of our common stock as of December 31, 2020. The market value as of December 31, 2020 was $11.73 per share, which was the closing price of our common stock reported for transactions effected on the NASDAQ Global Select Market on December 31, 2020, the final trading day of 2020.

Schedule of Assumptions used to Value PSUs Granted

The following table summarizes the assumptions used to value the PSUs granted during the years ended December 31, 2020, 2019 and 2018:

	Year Ended December 31,
	2020			2019			2018
Expected term (years)		3.0			3.0			3.0
Expected volatility		63.0	%		57.5	%		48.5	%
Expected annual dividend		0.0	%		0.0	%		0.0	%
Risk free rate		0.7	%		2.3	%		2.3	%