Employee Benefit Plans Employee Benefit Plans 17 (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Employer's contribution	$ 2.5	$ 2.4	$ 2.3
Employer discretionary contribution amount	$ 1.6	$ 1.3	$ 1.1