Income Taxes - NOL, foreign earnings (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Income Tax [Line Items]
Uncertain tax benefits against goodwill related to acquisition	$ 1.2
Internal Revenue Service (IRS) [Member]
Income Tax [Line Items]
Net operating loss carryforward	7.3
Canada Revenue Agency [Member]
Income Tax [Line Items]
Net operating loss carryforward	26.7
Mexican Tax Authority [Member]
Income Tax [Line Items]
Net operating loss carryforward	$ 8.9
Carryforward period	10 years