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Goodwill and Intangible Assets, Net - Goodwill - Narrative (Details)						2 Months Ended	6 Months Ended	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares	Nov. 05, 2018 USD ($)	Oct. 31, 2018 USD ($) $ / shares	Oct. 31, 2017 USD ($)	Sep. 30, 2017 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2018	Feb. 11, 2014 $ / shares
Goodwill [Line Items]
Goodwill	$ 422,513,000					$ 422,513,000		$ 422,513,000	$ 422,513,000
Accumulated impairment losses	$ 0					$ 0		$ 0
Share price (in dollars per share) \| $ / shares	$ 15.19		$ 21.50		$ 18.45	$ 15.19		$ 15.19				$ 20.07
Market capitalization		$ 633,000,000	$ 742,000,000		$ 653,000,000	$ 617,000,000
Fair value percentage below carrying amount, reporting unit	41.00%	20.00%	2.00%		18.00%	21.00%
Fair value percentage above carrying amount, net assets	15.00%		36.00%		6.00%
Goodwill, impairment			$ 0	$ 0	$ 0		$ 0	$ 0
Share price, median (in dollars per share) \| $ / shares						$ 17.84
Reporting unit, carrying amount	$ 747,000,000					$ 747,000,000		747,000,000
Impairment of intangible assets								$ 0	$ 319,246,000	$ 15,724,000
Fair value percentage above carrying amount, reporting unit				18.00%
Fair value inputs, discount rate, sensitivity analysis of one percent				1.00%
Measurement Input, Control Premium
Goodwill [Line Items]
Reporting unit, measurement input, median											0.71
Measurement Input, Control Premium \| Minimum
Goodwill [Line Items]
Reporting unit, measurement input					0.30						0.39
Measurement Input, Control Premium \| Maximum
Goodwill [Line Items]
Reporting unit, measurement input					0.83
Measurement Input, Control Premium \| Weighted Average
Goodwill [Line Items]
Reporting unit, measurement input					0.64
Measurement Input, Discount Rate \| Minimum
Goodwill [Line Items]
Reporting unit, measurement input				0.100
Measurement Input, Discount Rate \| Maximum
Goodwill [Line Items]
Reporting unit, measurement input				0.195							0.96
Measurement Input, Discount Rate \| Weighted Average
Goodwill [Line Items]
Reporting unit, measurement input				0.136