Defined Benefit Plans - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) plan	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Estimated unrecognized loss that will be amortized from AOCI, net of income taxes	$ 200
Number of plans | plan	3
Benefit obligation	$ 8,500	$ 9,300
Fair value of plan assets	$ 4,900	$ 5,500
Annual rate of return on plan assets	7.00%	7.00%
Estimated future benefit payments	$ 500
Minimum | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.00%	3.50%
Maximum | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.25%	4.00%
United Kingdom Subsidiary | UK Plan
Defined Benefit Plan Disclosure [Line Items]
Underfunded status of UK Plan	$ 17,582	$ 36,650
Annual rate of inflation	2.10%	2.10%
Average life expectancy	25 years
Estimated unrecognized loss that will be amortized from AOCI, net of income taxes	$ 1,900
Future estimated employer contributions to be paid next year	4,500
Benefit obligation	281,776	$ 332,618	$ 306,731
Fair value of plan assets	$ 264,194	$ 295,968	$ 257,236
Discount rate	2.90%	2.50%
Annual rate of return on plan assets	5.00%	5.30%	6.20%
Selling, General and Administrative Expenses | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Reclassification adjustment from AOCI, net of income taxes	$ 200	$ 200	$ 200
Selling, General and Administrative Expenses | United Kingdom Subsidiary | UK Plan
Defined Benefit Plan Disclosure [Line Items]
Reclassification adjustment from AOCI, net of income taxes	2,100	2,300	$ 1,700
Other Noncurrent Liabilities | United Kingdom Subsidiary | UK Plan
Defined Benefit Plan Disclosure [Line Items]
Underfunded status of UK Plan	$ 17,600	$ 36,700