Equity Incentive Plans and Stock-Based Compensation (Details) - shares		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Stock-Based Compensation
Tenure of award (in years)		10 years
Option One
Stock-Based Compensation
Requisite service period (in months)		60 months
Option Two
Stock-Based Compensation
Requisite service period (in months)		48 months
Stock compensation plan
Shares available for grant
Shares available, at the beginning of the year		6,826,863		10,074,046		5,051,147
Number of additional shares authorized		7,800,000	[1]	400,000	[2]	5,500,000
Stock options granted		(40,000)		(80,000)		(711,479)
Stock options forfeited		101,816		426,960		877,803
Nonvested equity stock and stock units granted (in shares)	[4]	(3,528,401)	[3]	(7,261,845)	[5]	(4,993,802)	[6]
Nonvested equity stock and stock units forfeited (in shares)	[4]	1,252,042		3,267,702		4,350,377
Shares available, at the end of the period		12,412,320		6,826,863		10,074,046
Conversion factor used to calculate the decrease in the number of shares available for grant resulting from the grant of restricted stock awards		1.5		1.5		1.5
Conversion factor used to calculate the increase in the number of shares available for grant resulting from the forfeiture of restricted stock awards		1.5		1.5		1.5
Potential additional performance stock units
Shares available for grant
Nonvested equity stock and stock units granted (in shares)		500,000		1,000,000.0		500,000

[1] On April 30, 2020, the Company’s stockholders approved an additional 7,800,000 shares for issuance under the 2015 Plan.

[2] Shares were reserved under the 2019 Inducement Plan adopted in the third quarter of 2019.

[3] Amount includes 0.5 million shares that have been reserved for potential future issuance related to certain performance unit awards discussed under the section titled “Nonvested Equity Stock and Stock Units” below.

[4] For purposes of determining the number of shares available for grant under the 2015 Plan against the maximum number of shares authorized, each restricted stock granted reduces the number of shares available for grant by 1.5 shares and each restricted stock forfeited increases shares available for grant by 1.5 shares.

[5] Amount includes 1.0 million shares that have been reserved for potential future issuance related to certain performance unit awards discussed under the section titled “Nonvested Equity Stock and Stock Units” below.

[6] Amount includes 0.5 million shares that had been reserved for potential future issuance related to certain performance unit awards discussed under the section titled “Nonvested Equity Stock and Stock Units” below.