Income Taxes - Additional Information (Details) € in Thousands, $ in Thousands			1 Months Ended			3 Months Ended				9 Months Ended		12 Months Ended		48 Months Ended
	Sep. 30, 2018 USD ($)	Jun. 29, 2012 EUR (€)	Oct. 31, 2018 USD ($)	Oct. 31, 2018 EUR (€)	Oct. 31, 2015 EUR (€)	Sep. 30, 2018 USD ($)	Mar. 31, 2018 EUR (€)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 EUR (€)	Dec. 31, 2013 audit	Dec. 31, 2017 EUR (€)
Operating Loss Carryforwards [Line Items]
Transition tax for accumulated foreign earnings, provisional income tax expense								$ 149,800
Transition tax for accumulated foreign earnings, provisional liability								3,200
Provisional income tax expense (benefit)								(66,900)
Change in tax rate, deferred tax asset, provisional income tax expense (benefit), net of adjustments								(70,700)
Benefit from release of valuation allowance for state conformity										$ 400
Income tax expense (benefit)						$ (3,773)			$ 12,530	$ 65,822	$ 13,668
Foreign Tax Authority | Tax Authority, Spain
Operating Loss Carryforwards [Line Items]
Number of tax audits (audit) | audit														2
Letters of credit outstanding, amount | €															€ 33,282
Income tax expense (benefit)												$ 42,100	€ 37,610
Income taxes paid	$ 34,800						€ 29,600
Tax Year 2006 Through 2008 | Foreign Tax Authority | Tax Authority, Spain
Operating Loss Carryforwards [Line Items]
Possible loss from tax audits	13,000	€ 11,051
Tax Year 2008 Through 2010 | Foreign Tax Authority | Tax Authority, Spain
Operating Loss Carryforwards [Line Items]
Possible loss from tax audits	$ 20,200				€ 17,187
Cash Collateralized Letter Of Credit - Spain Tax Audits
Operating Loss Carryforwards [Line Items]
Letters of credit outstanding, amount								$ 39,505
Subsequent Event | Tax Year 2011 Through 2013 | Foreign Tax Authority | Tax Authority, Spain
Operating Loss Carryforwards [Line Items]
Possible loss from tax audits			$ 4,800	€ 4,066