Debt - Line of Credit (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Oct. 27, 2014
Line of Credit Facility [Line Items]
Line of Credit Facility, Available Additional Borrowing Capacity		$ 300.0
Interest Paid	$ 29.2	27.2	$ 3.7
Payments of Debt Issuance Costs		6.9
Payments of Financing Costs		$ 2.2
Minimum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.125%
Maximum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.30%
Credit Agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 300.0
Credit Agreement [Member] | Adjusted Base Rate Advances [Member] | Adjusted Base Rate [Member] | Federal Funds Rate [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Basis Spread on Variable Rate	0.50%
Credit Agreement [Member] | Adjusted Base Rate Advances [Member] | Adjusted Base Rate [Member] | Eurodollar Rate [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Basis Spread on Variable Rate	1.00%
Credit Agreement [Member] | Adjusted Base Rate Advances [Member] | Applicable Margin [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Basis Spread on Variable Rate	0.125%
Credit Agreement [Member] | Adjusted Base Rate Advances [Member] | Applicable Margin [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Basis Spread on Variable Rate	0.75%
Credit Agreement [Member] | Eurodollar Advances [Member] | Applicable Margin [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Basis Spread on Variable Rate	1.125%
Line of Credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 500.0
Letter of Credit [Member] | Eurodollar Advances [Member] | Applicable Margin [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Basis Spread on Variable Rate	1.75%