Retirement Plans - Defined Benefit Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined benefit plan disclosures
Other income (expense), net	$ (368)	$ 392	$ (223)
Income tax expense (benefit)	$ (26,746)	$ (37,594)	2,823
Minimum pension liability | Reclassification out of AOCI
Defined benefit plan disclosures
Other income (expense), net			(900)
Income tax expense (benefit)			$ (400)