Stock-Based Compensation - Stock Option Activity (Details) - $ / shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Options outstanding, beginning balance (shares)	1,342,000
Options granted (in shares)	0	0	0
Options exercised (shares)	(119,000)
Options canceled/forfeited (shares)	(55,000)
Options outstanding, ending balance (shares)	1,168,000	1,342,000
Options vested of expected to vest (shares)	1,168,000
Options exercisable (shares)	1,168,000
Weighted Average Exercise Price per Share
Options outstanding, beginning balance (usd per share)	$ 11.84
Options granted (usd per share)	0
Options exercised (usd per share)	6.93
Options canceled/forfeited (usd per share)	23.75
Options outstanding, ending balance (usd per share)	11.77	$ 11.84
Options vested and expected to vest, weighted average exercise price (usd per share)	11.77
Options exercisable, weighted average exercise price (usd per share)	$ 11.77
Options outstanding, weighted average remaining contractual life (in years)	5 years	5 years 10 months 24 days
Options vested or expected to vest, weighted average remaining contractual life (in years)	5 years
Options exercisable, weighted average remaining contractual life (in years)	5 years

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.