Income Taxes - Net Operating Losses and Valuation Allowance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating losses carryforwards [Line Items]
Valuation allowance	$ 7.1	$ 6.0
Dividends Received Deduction Percentage	80.00%
Income taxes additional disclosure
Deferred taxes provided on unremitted earnings of unconsolidated affiliates	$ 0.0	6.5
Tax on distribution of foreign earnings	1.0	1.0	$ 1.9
Income tax liability, net of credits, on unremitted earnings	2.3	2.6
Accumulated undistributed earnings of foreign subsidiaries	186.2
Federal
Income taxes additional disclosure
Tax on distribution of foreign earnings	1.0	1.0	$ 1.9
Federal | Business combinations
Operating losses carryforwards [Line Items]
Net operating losses carryforwards	4.1
State
Operating losses carryforwards [Line Items]
Valuation allowance	0.2	0.3
State | Business combinations
Operating losses carryforwards [Line Items]
Net operating losses carryforwards	48.4
International jurisdictions
Operating losses carryforwards [Line Items]
Net operating losses carryforwards	53.9
Valuation allowance	6.9	$ 5.7
Canada | International jurisdictions
Operating losses carryforwards [Line Items]
Net operating losses carryforwards	4.4
U.K. | International jurisdictions
Operating losses carryforwards [Line Items]
Net operating losses carryforwards	23.4
Ireland | International jurisdictions
Operating losses carryforwards [Line Items]
Net operating losses carryforwards	13.1
Australia | International jurisdictions
Operating losses carryforwards [Line Items]
Net operating losses carryforwards	$ 13.0