Significant Accounting Policies (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Stock-based compensation expense	$ 993,000	$ 1,166,000	$ 1,935,000	$ 1,456,000
Operating lease right-of-use assets	65,571,000		65,571,000			$ 0
Operating lease liability	66,550,000		66,550,000
Cumulative-effect adjustment for the adoption of ASU 2016-02							$ 0
Reclassification out of property, plant and equipment	256,900,000		256,900,000			264,960,000
Reclassification into other assets	11,623,000		$ 11,623,000			7,660,000
Software | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life			3 years
Software | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life			10 years
Cloud Computing Arrangements | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life			3 years
Cloud Computing Arrangements | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life			10 years
Prepaid and other current assets
Finite-Lived Intangible Assets [Line Items]
Implementation costs	300,000		$ 300,000
Other assets
Finite-Lived Intangible Assets [Line Items]
Implementation costs	$ 4,100,000		$ 4,100,000
Accounting Standards Update 2016-02
Finite-Lived Intangible Assets [Line Items]
Operating lease right-of-use assets					$ 69,000,000
Operating lease liability					69,000,000
Cumulative-effect adjustment for the adoption of ASU 2016-02						$ 0
Accounting Standards Update 2018-15
Finite-Lived Intangible Assets [Line Items]
Reclassification out of property, plant and equipment					(2,800,000)
Reclassification into other assets					$ 2,800,000