Goodwill and Intangible Assets - Estimated Future Amortization Expense by Year (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 14,000	$ 16,100	$ 16,400
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2019	13,641
2020	13,603
2021	13,400
2022	13,400
2023	$ 13,270