Debt (Schedule Of Carrying And Principal Values Of Debt) (Details) - USD ($)								12 Months Ended
	Oct. 13, 2017	Apr. 17, 2017	Jul. 07, 2016	Oct. 14, 2015	Oct. 15, 2014	Apr. 18, 2013	Aug. 09, 2012	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Principal Balance								$ 9,405,000,000	$ 8,875,000,000
Fair Value								9,436,290,000	8,844,682,000
Carrying Value								9,310,686,000	8,775,583,000
Less: current maturities of long-term debt								(20,000,000)	(627,157,000)
Total long-term debt, net of current maturities								9,290,686,000	8,148,426,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal Balance								40,000,000	390,000,000
Fair Value								40,000,000	390,000,000
Carrying Value								$ 40,000,000	390,000,000
Debt instrument, maturity date								Feb. 05, 2020
2014 Senior Notes [Member]
Debt Instrument [Line Items]
Principal Balance								$ 750,000,000	750,000,000
Fair Value								770,625,000	763,125,000
Carrying Value								$ 739,079,000	736,992,000
Debt instrument, maturity date								Jul. 15, 2022
2016 Senior Notes [Member]
Debt Instrument [Line Items]
Principal Balance								$ 1,100,000,000	1,100,000,000
Fair Value								1,127,500,000	1,083,500,000
Carrying Value								$ 1,081,262,000	1,078,954,000
Debt instrument, maturity date								Sep. 01, 2024
2017 Senior Notes [Member]
Debt Instrument [Line Items]
Principal Balance								$ 750,000,000
Fair Value								750,938,000
Carrying Value								$ 741,437,000
Debt instrument, maturity date	Oct. 01, 2022							Oct. 01, 2022
2012-1C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance									610,000,000
Fair Value									610,165,000
Carrying Value									607,157,000
Debt instrument, maturity date							Dec. 09, 2042	Dec. 11, 2017
2013-1C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 425,000,000	425,000,000
Fair Value								423,853,000	423,381,000
Carrying Value								$ 424,482,000	422,768,000
Debt instrument, maturity date						Apr. 09, 2043		Apr. 10, 2018
2013-2C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 575,000,000	575,000,000
Fair Value								578,433,000	563,322,000
Carrying Value								$ 568,609,000	567,545,000
Debt instrument, maturity date						Apr. 09, 2048		Apr. 11, 2023
2013-1D Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 330,000,000	330,000,000
Fair Value								330,145,000	334,521,000
Carrying Value								$ 329,585,000	328,225,000
Debt instrument, maturity date						Apr. 09, 2043		Apr. 10, 2018
2014-1C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 920,000,000	920,000,000
Fair Value								915,216,000	922,199,000
Carrying Value								$ 914,929,000	912,219,000
Debt instrument, maturity date					Oct. 11, 2044			Oct. 08, 2019
2014-2C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 620,000,000	620,000,000
Fair Value								620,942,000	608,921,000
Carrying Value								$ 613,461,000	612,641,000
Debt instrument, maturity date					Oct. 08, 2049			Oct. 08, 2024
2015-1C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 500,000,000	500,000,000
Fair Value								496,840,000	495,145,000
Carrying Value								$ 493,474,000	491,289,000
Debt instrument, maturity date				Oct. 10, 2045				Oct. 08, 2020
2016-1C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 700,000,000	700,000,000
Fair Value								691,166,000	688,072,000
Carrying Value								$ 693,118,000	691,322,000
Debt instrument, maturity date			Jul. 10, 2046					Jul. 09, 2021
2017-1C Tower Securities [Member]
Debt Instrument [Line Items]
Principal Balance								$ 760,000,000
Fair Value								751,404,000
Carrying Value								$ 751,076,000
Debt instrument, maturity date		Apr. 09, 2047						Apr. 11, 2022
2014 Term Loan [Member]
Debt Instrument [Line Items]
Principal Balance								$ 1,447,500,000	1,462,500,000
Fair Value								1,451,119,000	1,467,984,000
Carrying Value								$ 1,439,373,000	1,452,039,000
Debt instrument, maturity date								Mar. 24, 2021
2015 Term Loan [Member]
Debt Instrument [Line Items]
Principal Balance								$ 487,500,000	492,500,000
Fair Value								488,109,000	494,347,000
Carrying Value								$ 480,801,000	$ 484,432,000
Debt instrument, maturity date								Jun. 10, 2022