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Long-term Debt (Details) $ in Thousands					9 Months Ended	12 Months Ended
	Sep. 22, 2017 Rate	Aug. 22, 2017 Rate	Feb. 21, 2017 USD ($) Rate	Aug. 05, 2016 Rate	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 05, 2015 USD ($)
Debt Instrument [Line Items]
Unamortized deferred loan costs | $					$ 13,503	$ 15,645
Long-term Debt | $					609,997	640,355
Credit facility amendment costs | $					$ 3,300	$ 900
Contractual Quarterly Payments | $							$ 2,100
Leverage Ratio					2.08
$825 Million Term B Loan Facility and $150 Million Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount | $							975,000
$825 Million Term B Loan Facility, due June 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount | $							825,000
$150 Million Revolving Credit Facility, Due June 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount | $							$ 150,000
$200 Million Revolving Credit Facility, Due February 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount | $			$ 200,000
Maximum [Member]
Debt Instrument [Line Items]
Leverage Ratio in Latest Year of Debt Term					3.25
Leverage Ratio					4.00
Notes Payable to Banks [Member] | $825 Million Term B Loan Facility, due June 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate | Rate		0.25%	0.50%	0.25%
Notes Payable to Banks [Member] | $200 Million Revolving Credit Facility, Due February 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate | Rate	0.50%
Notes Payable to Banks [Member] | Minimum [Member] | $200 Million Revolving Credit Facility, Due February 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate | Rate	0.25%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | Rate	0.20%
Line of Credit Facility, Commitment Fee Percentage | Rate	0.05%
Notes Payable to Banks [Member] | Minimum [Member] | Eurodollar [Member] | $200 Million Revolving Credit Facility, Due February 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate | Rate	1.25%
Notes Payable to Banks [Member] | Maximum [Member] | $200 Million Revolving Credit Facility, Due February 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate | Rate	1.25%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | Rate	0.35%
Notes Payable to Banks [Member] | Maximum [Member] | Eurodollar [Member] | $825 Million Term B Loan Facility, due June 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate | Rate		2.00%
Notes Payable to Banks [Member] | Maximum [Member] | Eurodollar [Member] | $200 Million Revolving Credit Facility, Due February 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate | Rate	2.25%
$200 Million Revolving Credit Facility, Due February 2022 [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity | $					$ 166,600
Interest Expense [Member]
Debt Instrument [Line Items]
Credit facility amendment costs | $					$ 2,700

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