Pension plan and 401(k) Program - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Retirement Benefits [Abstract]
Company contributions			$ 0.8
Expected future employer contributions, next fiscal year	$ 1.6		$ 1.6
Employer's matching contribution, percent of match			50.00%
Employer's matching contribution, percent of employee's gross pay			6.00%
Employers matching contribution vesting percentage after two years of credited service			50.00%
Employers matching contribution vesting percentage after three years of credited service			100.00%
401k plan expense	$ 0.7	$ 0.8	$ 1.5	$ 1.5