Segment and Geographic Information - Segment income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information
Sales to external customers	$ 342.4	$ 357.8	$ 309.6	$ 289.3	$ 290.1	$ 272.2	$ 277.9	$ 244.1	$ 1,299.1	$ 1,084.3	$ 842.9
Depreciation and amortization expense									78.8	50.8	37.6
Operating income (loss)	$ 21.1	$ 29.9	$ 25.3	$ 4.6	$ 26.3	$ 31.5	$ 19.3	$ 15.0	80.9	92.1	38.5
Capital expenditures									36.2	35.6	33.0
Operating Segments | D&S East
Segment Reporting Information
Sales to external customers									293.4	246.3	232.3
Depreciation and amortization expense									16.6	11.1	9.5
Operating income (loss)									6.9	19.3	14.2
Capital expenditures									14.8	10.4	11.1
Operating Segments | D&S West
Segment Reporting Information
Sales to external customers									461.7	455.5	400.6
Depreciation and amortization expense									11.6	11.2	10.6
Operating income (loss)									104.5	101.2	85.2
Capital expenditures									8.7	6.0	4.1
Operating Segments | E&C Cryogenics
Segment Reporting Information
Sales to external customers									190.2	136.9	125.5
Depreciation and amortization expense									14.5	10.9	10.3
Operating income (loss)									1.6	1.8	(2.1)
Capital expenditures									4.5	12.1	14.1
Operating Segments | E&C FinFans
Segment Reporting Information
Sales to external customers									361.7	253.6	100.1
Depreciation and amortization expense									34.5	16.1	5.0
Operating income (loss)									40.6	23.7	7.2
Capital expenditures									3.1	3.4	1.4
Intersegment Eliminations
Segment Reporting Information
Sales to external customers									(7.9)	(8.0)	(15.6)
Depreciation and amortization expense									0.0	0.0	0.0
Operating income (loss)									(2.3)	(2.5)	(3.6)
Capital expenditures									0.0	0.0	0.0
Corporate
Segment Reporting Information
Sales to external customers									0.0	0.0	0.0
Depreciation and amortization expense									1.6	1.5	2.2
Operating income (loss)									(70.4)	(51.4)	(62.4)
Capital expenditures									$ 5.1	$ 3.7	$ 2.3