Fair Value Measurements - Summary of Fair Values Principal Balances and Carrying Values of Company's Debt Instruments (Parenthetical) (Detail)	Mar. 31, 2013	Sep. 28, 2012
1.875% Convertible Senior Notes [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Interest rates for senior notes	1.875%
4.000% Convertible Senior Notes [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Interest rates for senior notes	4.00%
8.250% Senior Notes [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Interest rates for senior notes	8.25%
5.625% Senior Notes [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Interest rates for senior notes	5.625%	5.625%
5.750% Senior Notes [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Interest rates for senior notes	5.75%
2.933% Secured Tower Revenue Securities Series 2012-1 [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Interest rates for senior notes	2.933%
4.254% 2010-1C Tower Securities [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Interest rates for senior notes	4.254%
5.101% 2010-2C Tower Securities [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Interest rates for senior notes	5.101%