Debt (Schedule Of Cash And Non-Cash Interest Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 15, 2016	Jul. 07, 2016	Oct. 14, 2015	Sep. 28, 2012	Aug. 09, 2012	Jul. 13, 2012	Apr. 16, 2010	Jul. 24, 2009	Apr. 24, 2009
Debt Instrument [Line Items]
Cash Interest	$ 329,171	$ 322,366	$ 292,600
Non-cash Interest	2,203	1,505	27,112
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Cash Interest	$ 4,167	5,552	4,591
4.0% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest			12,520
Non-cash Interest			26,266
Debt instrument, interest rate, stated percentage	4.00%											4.00%
8.25% Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest			12,513
Non-cash Interest			$ 121
Debt instrument, interest rate, stated percentage	8.25%		8.25%								8.25%
5.625% Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest	$ 21,094	28,125	$ 28,125
Debt instrument, interest rate, stated percentage	5.625%						5.625%
5.75% Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest	$ 28,494	46,000	46,000
Debt instrument, interest rate, stated percentage	5.75%								5.75%
2014 Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest	$ 36,563	36,563	18,281
Non-cash Interest	689	655	315
2016 Senior Notes [Member]
Debt Instrument [Line Items]
Cash Interest	20,258
Non-cash Interest	348
Debt instrument, interest rate, stated percentage				4.875%
2010 Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	15,213	28,230	51,237
2010-2C Tower Securities [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage										5.101%
2012-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	18,107	18,111	18,085
Debt instrument, interest rate, stated percentage								2.933%
2013 Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	43,217	43,217	43,217
2014 Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	51,138	51,138	10,796
2015-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	15,939	3,453
Debt instrument, interest rate, stated percentage						3.156%
2016-1C Tower Securities [Member]
Debt Instrument [Line Items]
Cash Interest	9,898
Debt instrument, interest rate, stated percentage					2.877%
2011 Term Loan [Member]
Debt Instrument [Line Items]
Cash Interest			696
Non-cash Interest			7
2012-1 Term Loan [Member]
Debt Instrument [Line Items]
Cash Interest		3,959	4,534
2012-2 Term Loan [Member]
Debt Instrument [Line Items]
Cash Interest			424
Non-cash Interest			4
2014 Term Loan [Member]
Debt Instrument [Line Items]
Cash Interest	48,962	48,992	41,338
Non-cash Interest	510	492	399
2015 Term Loan [Member]
Debt Instrument [Line Items]
Cash Interest	16,487	9,243
Non-cash Interest	656	358
Other [Member]
Debt Instrument [Line Items]
Cash Interest	$ (366)	$ (217)	$ 243