Intangible Assets - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 6,200,000	$ 6,500,000	$ 12,400,000	$ 12,900,000
Goodwill [Line Items]
Goodwill	1,432,787,000	$ 1,409,276,000	1,432,787,000	$ 1,409,276,000	$ 1,432,787,000	$ 1,386,853,000
Non-Strategic
Goodwill [Line Items]
Gross goodwill	200,000,000.0		200,000,000.0		200,000,000
Accumulated impairments	114,100,000		114,100,000		114,100,000
Accumulated divestiture related write-offs	85,900,000		85,900,000		85,900,000
Goodwill	$ 0		$ 0		$ 0