Employee Stock Plans - Stock Award Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Stock Option Activity
Outstanding beginning balance (in shares)	2,412,000
Granted (in shares)	50,000	0
Exercised (in shares)	(634,000)
Expired or canceled (in shares)	(8,000)
Outstanding ending balance (in shares)	1,820,000	2,412,000
Stock Option Weighted Average Exercise Price Per Share
Outstanding begging balance (in dollars per share)	$ 13.58
Granted (in dollars per share)	24.62
Exercised (in dollars per share)	10.23
Expired or canceled (in dollars per share)	18.15
Outstanding ending balance (in dollars per share)	$ 15.02	$ 13.58
Stock Option Activity, Additional Disclosures
Options outstanding, Weighted average remaining contractual term	2 years 3 months 10 days
Options outstanding, Aggregate intrinsic value (in dollars)	$ 21.1
Options vested and exercisable, Number of Options (in shares)	1,375,000
Options vested and exercisable, Weighted average exercise price per share (in dollars per share)	$ 14.00
Options vested and exercisable, Weighted average remaining contractual term	2 years 14 days
Options exercisable, Aggregate intrinsic value (in dollars)	$ 17.3