Fair Value Measurements (Carrying Amount And The Estimated Fair Value Of Financial Instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents, Carrying Amount	$ 92,449	$ 66,655	$ 84,958	$ 82,306
Accounts receivable, Carrying Amount	276,378	$ 280,858
Cash and cash equivalents, Fair Value	92,449
Accounts receivable, Fair Value	276,378
Quoted in Markets Identical (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Senior Credit Facilities, Carrying Amount (Level 1)	1,769,625
Senior Credit Facilities, Fair Value (Level 1)	1,791,643
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Senior Notes, Carrying Amount (Level 2)	981,795
Senior Notes, Fair Value (Level 2)	$ 1,062,969