Debt (Schedule Of Cash And Non-Cash Interest Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Apr. 17, 2017	Aug. 15, 2016	Jul. 07, 2016	Oct. 14, 2015	Jul. 01, 2014	Aug. 09, 2012
Debt Instrument [Line Items]
Cash Interest	$ 78,456	$ 83,682	$ 156,058	$ 167,486
Non-cash Interest	717	460	1,421	915
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Cash Interest	$ 1,406	744	$ 4,176	1,578
5.625% Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest		7,031		14,063
Debt instrument, interest rate, stated percentage	5.625%		5.625%			5.625%
5.75% Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest		11,500		23,000
Debt instrument, interest rate, stated percentage	5.75%		5.75%			5.75%
2014 Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest	$ 9,141	9,141	$ 18,281	18,281
Non-cash Interest	180	171	357	340
Debt instrument, interest rate, stated percentage									4.875%
2016 Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest	13,406		26,813
Non-cash Interest	237		471
Debt instrument, interest rate, stated percentage						4.875%
2010-2C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest		7,058		14,115
2012-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	806	4,533	5,331	9,067
Debt instrument, interest rate, stated percentage										2.933%
2013 Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	10,804	10,804	21,609	21,609
2014 Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	12,785	12,785	25,569	25,569
2015-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	3,985	3,985	7,969	7,969
Debt instrument, interest rate, stated percentage								3.156%
2016-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	5,090		10,181
Debt instrument, interest rate, stated percentage							2.877%
2017-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	5,001		5,001
Debt instrument, interest rate, stated percentage					3.168%
2014 Term Loan [Member]
Debt Instrument [Line Items]
Cash Interest	12,043	12,107	23,327	24,245
Non-cash Interest	131	126	259	251
2015 Term Loan [Member]
Debt Instrument [Line Items]
Cash Interest	4,056	4,077	7,855	8,164
Non-cash Interest	169	163	334	324
Other [Member]
Debt Instrument [Line Items]
Cash Interest	$ (67)	$ (83)	$ (54)	$ (174)