Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies - Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Intangible Assets Net Excluding Goodwill [Abstract]
Indefinite-lived intangible asset	$ 45,275	$ 45,275
Amortizing intangible asset, Gross carrying value	84,871	84,871
Amortizing intangible asset, Accumulated amortization	(78,633)	(75,231)
Amortizing intangible asset, Net carrying amount	6,238	9,640
Total intangible assets, Gross carrying amount	130,146	130,146
Total intangible assets, Net carrying amount	$ 51,513	$ 54,915