Debt Narrative (Details)		3 Months Ended		9 Months Ended
	Dec. 01, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Line of Credit Facility [Line Items]
Borrowings		$ 595,500,000		$ 595,500,000
Interest expense			$ 0		$ 0
Amortization of debt issuance costs				1,818,000	$ 0
Repayment of debt		1,500,000		4,500,000
Term B Loan Facility | Line of Credit
Line of Credit Facility [Line Items]
Debt instrument, covenant, maximum ratio	1.50
Quarterly payment as a percentage of principal	0.25%
Debt instrument, maturity date	Nov. 30, 2023
Borrowings	$ 600,000,000	$ 595,500,000		$ 595,500,000
Interest rate		4.90%		4.90%
Unamortized debt issuance costs		$ 14,900,000		$ 14,900,000
Interest expense		7,400,000		20,900,000
Amortization of debt issuance costs		$ 600,000		$ 1,800,000
Term B Loan Facility | Line of Credit | Base Rate
Line of Credit Facility [Line Items]
Debt instrument, description of variable rate basis	base rate
Term B Loan Facility | Line of Credit | Base Rate | Effective Date Margin
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.25%
Term B Loan Facility | Line of Credit | Base Rate | Margin Subject to Debt Covenant
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.00%
Term B Loan Facility | Line of Credit | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Debt instrument, description of variable rate basis	LIBOR
Term B Loan Facility | Line of Credit | London Interbank Offered Rate (LIBOR) | Effective Date Margin
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	3.25%
Term B Loan Facility | Line of Credit | London Interbank Offered Rate (LIBOR) | Margin Subject to Debt Covenant
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	3.00%
Term B Loan Facility | Line of Credit | Royal Bank of Canada
Line of Credit Facility [Line Items]
Borrowing capacity	$ 600,000,000
Loan facility, term	7 years