401(k) Plan 401(k) Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
401(k) Plan [Abstract]
Maximum contribution % of eligible pre-tax compensation allowed to participants of defined contribution plan	50.00%
Employer match	$ 6.6	$ 6.3	$ 7.0
Employer match, percent	50.00%
Employer match, percent of employees' compensation	6.00%
Percent of company stock purchased	8.20%	6.20%