Stock Award Plans and Stock Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	May 12, 2012	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	May 02, 2012
Stock-Based Compensation
Common stock, par value (in dollars per share)		$ 0.001	$ 0.001
Stock-Based Compensation Expense
Forfeiture rate (as a percent)		5.00%	5.00%	5.00%
Stock-based compensation expense		$ 12,100	$ 10,500	$ 8,200
Tax deductions in excess of recognized compensation cost		18,700
Tax benefit		$ 3,900
Estimated weighted-average assumptions
Weighted-average expected volatility (as a percent)		53.07%
Weighted-average expected term		4 years 8 months 15 days
Risk-free interest rate		1.22%
Expected dividend yield (as a percent)		0.00%
Options
Granted (in shares)			0	0
Common Stock
Employee Stock Purchase Plan
Number of shares purchased under the plan		26,000	41,000	54,000
Options
Exercised (in shares)		(396,000)	(1,001,000)	(775,000)
Employee Stock Purchase Plan
Stock-Based Compensation
Number of shares of common stock originally reserved for future grant		1,000,000.0
Employee Stock Purchase Plan
Purchase price as a percentage of the market value of a common stock on the day the stock is purchased		85.00%
Offering period over which compensation expense is amortized		6 months
Number of shares purchased under the plan		10,588
Stock-Based Compensation Expense
Stock-based compensation expense		$ 200	$ 200	$ 200
Employee Stock Purchase Plan | Maximum
Employee Stock Purchase Plan
Payroll deductions as a percentage of employee's salary		10.00%
Restricted Stock Units
Shares/units
Outstanding at the beginning of the period (in shares)		1,089,000
Granted (in shares)		318,000
Vested (in shares)		(496,000)
Forfeited (in shares)		(12,000)
Outstanding at the end of the period (in shares)		899,000	1,089,000
Weighted-Average Grant Date Fair Value per Share
Outstanding at the beginning of the period (in dollars per share)		$ 20.77
Granted (in dollars per share)		38.54	$ 23.60	$ 17.08
Vested (in dollars per share)		21.32
Forfeited (in dollars per share)		19.76
Outstanding at the end of the period (in dollars per share)		$ 26.74	$ 20.77
Restricted Stock Units | Employees
Stock-Based Compensation
Vesting period		4 years
Restricted Stock Units | Non-employee members of Board of Director
Stock-Based Compensation
Vesting period		6 months
Stock Option Awards
Options
Outstanding at the beginning of the period (in shares)		504,000
Granted (in shares)		3,000
Vested (in shares)		0
Exercised (in shares)		(396,000)
Outstanding at the end of the period (in shares)		111,000	504,000
Exercisable (in shares)		108,000
Options Vested at the end of the period (in shares)		108,000
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)		$ 9.93
Granted (in dollars per share)		61.81
Exercised (in dollars per share)		9.31
Outstanding at the end of the period (in dollars per share)		13.51	$ 9.93
Exercisable at the end of the period (in dollars per share)		12.17
Options Vested at the end of the period (in dollars per share)		$ 12.17
Weighted Average Remaining Contractual Term
Outstanding at the end of the period		8 months 23 days
Exercisable at the end of the period		6 months 21 days
Options Vested at the end of the period		6 months 21 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)		$ 6,792
Exercisable at the end of the period (in dollars)		6,753
Options Vested at the end of the period (in dollars)		6,753
Additional disclosure
Total intrinsic value of options exercised (in dollars)		12,800	$ 18,400	$ 10,900
Total fair value of stock options vested (in dollars)			$ 100	$ 900
Stock Option Awards | Maximum
Additional disclosure
Total forfeiture adjusted unrecognized compensation cost (in dollars)		$ 100
Stock Option Awards | Employees
Stock-Based Compensation
Vesting period		4 years
Period after termination to exercise awards that were vested		90 days
Period after termination to retiring employees to exercise vested awards		1 year
Stock Option Awards | Non-employee members of Board of Director
Stock-Based Compensation
Vesting period		6 months
Restricted stock
Shares/units
Granted (in shares)		0	0	0
Vested (in shares)		0	0	0
Stock plan 2000 | Maximum
Employee Stock Purchase Plan
Number of shares purchased under the plan		100,000		100,000
Equity incentive plan 2012
Stock-Based Compensation
Number of shares of common stock originally reserved for future grant					9,500,000
Common stock, par value (in dollars per share)					$ 0.001
Number of shares of common stock available for future grants		1,500,000
Number of shares approved	7,760,000
Shares from expirations or forfeitures	1,780,000
Options
Outstanding at the end of the period (in shares)		100,000
Shares/units
Outstanding at the end of the period (in shares)		900,000
Equity incentive plan 2012 | Restricted Stock Units
Additional disclosure
Total forfeiture adjusted unrecognized compensation cost (in dollars)		$ 18,500
Weighted-average period over which unrecognized compensation cost is expected to be recognized		2 years 4 months 24 days
Equity incentive plan 2012 | Stock Option Awards
Stock-Based Compensation
Options Expiration period		7 years
Equity incentive plan 2012 | Restricted stock
Shares/units
Granted (in shares)		0	0	0
2000 ESPP and 2020 ESPP | Employee Stock Purchase Plan | Maximum
Employee Stock Purchase Plan
Number of shares purchased under the plan			100,000	100,000