Long-Term Debt Long-term Debt Text (Details) $ in Thousands			1 Months Ended	3 Months Ended	12 Months Ended
	Feb. 21, 2017 USD ($) Rate	Aug. 05, 2016 Rate	Jun. 15, 2015 Rate	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 05, 2015 USD ($)
Debt Instrument [Line Items]
Long-term Debt				$ 617,068	$ 640,355
Unamortized deferred loan costs				14,932	15,645
Credit facility amendment costs				$ 2,600	$ 900
Debt Instrument, Interest Rate, Stated Percentage				3.20%
Contractual Quarterly Payments				$ 2,100
Leverage Ratio				2.21
Letters of Credit Outstanding, Amount				$ 4,000
$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] | Minimum [Member] | $825 Million Term B Loan Facility, due June 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate | Rate	0.50%	0.25%
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			0.75%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | Rate			0.25%
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			2.50%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | Rate			0.40%
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			2.25%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity				$ 196,000
Interest Expense [Member]
Debt Instrument [Line Items]
Credit facility amendment costs				$ 2,000