Fair Value Measurement (Carrying Values And Fair Values Of The Company's Financial Instruments) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 3,101,138	$ 3,099,257
Long-term Debt, Fair Value	3,112,375	3,166,375
Term-A Facility [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	737,774	737,140
Long-term Debt, Fair Value	748,125	748,125
4.75% Senior Notes Due 2025 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	785,171	784,757
Long-term Debt, Fair Value	771,000	793,000
5.00% Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	984,591	984,056
Long-term Debt, Fair Value	988,750	1,012,500
4.75% Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	593,602	593,304
Long-term Debt, Fair Value	$ 604,500	$ 612,750