Significant Accounting Policies - Impairment of Long-Lived Assets (Details) - USD ($) $ in Thousands	3 Months Ended					12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of definite-lived assets		$ 7,100
Asset impairments						$ 3,087	$ 10,155	$ 0
Property, plant and equipment
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges						$ 2,900
FMT
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairments	$ 2,500
Operating lease, impairment	900
FMT | Corporate Office
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairments	600
FMT | Property, plant and equipment
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairments	1,600
FMT | Property, plant and equipment | Corporate Office
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairments	200
Operating lease, impairment	$ 400
HST
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment charges					$ 9,700
Operating lease, impairment			$ 400	$ 600
HST | Customer relationships
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of definite-lived assets					6,100
HST | Unpatented technology
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of definite-lived assets					1,000
HST | Property, plant and equipment
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairments					$ 2,000