Recent Accounting Pronouncements Recent Accounting Pronouncements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess Tax Benefit from Share-based Compensation, Operating Activities	$ 2.7
Excess Tax Benefit from Share-based Compensation, Financing Activities	0.0	$ 3.2	$ 3.4
Cumulative Effect on Retained Earnings, Net of Tax	1.0
Estimate of Revenue Recognized on Open Contracts Prior to Adoption of Revenue ASU [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	40.0
Estimated Income Statement Reclassification of Postretirement Costs from Operating to Non-Operating for Adoption on ASU 2017-07 on Jan 1 2018 [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	10.0	$ 18.0
Estimate of Operating Income Recognized on Open Contracts Prior to Adoption of Revenue ASU [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	5.0
Cumulative Effect Adjustment to Retained Earnings for Previously Recognized Income on Open Contracts, Net of Tax, Prior to Adoption of Revenue ASU [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	4.0
Accounting Standards Update 2016-09 [Member] | Deferred Tax Asset [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	(25.6)
Accounting Standards Update 2016-09 [Member] | Valuation Allowance, Operating Loss Carryforwards [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	23.5
Accounting Standards Update 2016-09 [Member] | Previously Unrecognized Tax Benefits Due to NOL Carryforwards [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax	2.1
Accounting Standards Update 2016-09 [Member] | Forfeiture Rate Estimate Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 1.1