Pension plan and 401(k) Program - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Retirement Benefits [Abstract]
Company contributions	$ 0.4
Expected future employer contributions, next fiscal year	$ 1.7
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	$ 0.8	$ 0.7

Defined Contribution Plan, Employers Matching Contribution Vesting Percentage After Three Years Of Credited Service

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Defined Contribution Plan, Employers Matching Contribution Vesting Percentage After Two Years Of Credited Service

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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.

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Amount of cost for defined contribution plan.

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Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

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Percentage employer matches of the employee's percentage contribution matched.

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