Commitments and Contingencies - Additional Information (Details) £ in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($) $ / £	Sep. 30, 2019 GBP (£) $ / £
Commitments And Contingencies [Line Items]
Purchase Commitments	$ 26.1
Long-term purchase commitment, Amount	$ 72.7
Pension Plan, Defined Benefit
Commitments And Contingencies [Line Items]
Defined benefit plan, estimated future employer contributions in current fiscal year, description	We have a contributory defined benefit plan that covers certain employees in the United Kingdom.  As of September 30, 2019, the unfunded liability for this defined benefit plan was approximately $33.0 million.  We are obligated to make annual contributions, each year through December 2029, of approximately GBP 2 million (approximately $2.6  million based on a GBP: USD exchange rate of 1.3:1).  It is necessary for the Trustees to review the contributions required to fund the benefits promised to the employees at least every three years.  A review as of April 2019 is underway and the outcome of the review could result in a change in the amount of the payment or the period over which payment is required.
Defined benefit plan, expected future benefit payments in year one	$ 2.6	£ 2
Defined benefit plan, expected future benefit payments in year two	2.6	2
Defined benefit plan, expected future benefit payments in year three	2.6	2
Defined benefit plan, expected future benefit payments in year four	2.6	2
Defined benefit plan, expected future benefit payments in year five	2.6	2
Defined benefit plan, expected future benefit payments in eight fiscal years thereafter	$ 2.6	£ 2
GBP:USD exchange rate | $ / £	1.3	1.3
Unfunded liability of defined benefit plan	$ 33.0