Retirement Plans - Defined Benefit Plans (Details) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans
Amounts included in accumulated other comprehensive loss
Unrecognized actuarial losses (gross)	$ 49,300,000	$ 48,800,000
Unrecognized actuarial losses (net of tax)	39,600,000	38,000,000.0
Unrecognized prior service cost (gross)	1,000,000.0	1,300,000
Unrecognized prior service cost (net of tax)	800,000	1,100,000
Projected benefit obligation
Beginning of year	182,800,000	172,500,000
Service cost	3,100,000	2,600,000	$ 3,400,000
Interest cost	5,500,000	5,300,000	5,400,000
Plan amendments	0	700,000
Actuarial (gain)/loss	(10,000,000.0)	15,500,000
Benefits paid	(13,900,000)	(13,800,000)
End of year	167,500,000	182,800,000	172,500,000
Fair value of plan assets
Beginning of year	165,700,000	163,200,000
Actual return on plan assets	(4,600,000)	14,900,000
Company contributions		0
Benefits paid	(13,900,000)	(13,800,000)
End of year	148,600,000	165,700,000	$ 163,200,000
(Unfunded) funded status end of year	(18,900,000)	(17,100,000)
Accumulated benefit obligation at end of year	167,000,000.0	181,100,000
Executive supplemental and director defined benefit pension plans
Projected benefit obligation
Beginning of year	22,300,000
End of year	19,600,000	22,300,000
Fair value of plan assets
Beginning of year	0
Company contributions	1,400,000	1,400,000
End of year	0	0
Accumulated benefit obligation at end of year	$ 19,100,000	$ 20,700,000

The after tax net amount of gains and losses that are not yet recognized as a component of net periodic benefit cost, and that are recognized as increases or decreases in other comprehensive income as they arise. Gains and losses are due to changes in the value of either the benefit obligation or the plan assets resulting from experience different from that assumed or from a change in an actuarial assumption, or the consequence of a decision to temporarily deviate from the substantive plan.

No definition available.