Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2013

Fair Value Disclosures [Abstract]

Summary of Fair Values, Principal Balances, and Carrying Values of Company's Debt Instruments

The following table reflects fair values, principal balances, and carrying values of the Company’s debt instruments (see Note 9).

	As of June 30, 2013						As of December 31, 2012
			Principal		Carrying				Principal		Carrying
	Fair Value		Balance		Value		Fair Value		Balance		Value
	(in millions)
1.875% Convertible Senior Notes	$	—	$	—	$	—	$	714,096	$	468,836	$	457,351
4.000% Convertible Senior Notes		1,227,459		499,973		448,988		1,060,622		499,987		430,751
8.250% Senior Notes		263,250		243,750		242,295		272,391		243,750		242,205
5.625% Senior Notes		495,000		500,000		500,000		523,750		500,000		500,000
5.750% Senior Notes		796,000		800,000		800,000		848,000		800,000		800,000
4.254% Secured Tower Revenue Securities Series 2010-1		699,149		680,000		680,000		713,619		680,000		680,000
5.101% Secured Tower Revenue Securities Series 2010-2		593,868		550,000		550,000		621,379		550,000		550,000
2.933% Secured Tower Revenue Securities Series 2012-1		613,983		610,000		610,000		635,614		610,000		610,000
2.240% Secured Tower Revenue Securities Series 2013-1C		413,865		425,000		425,000		—		—		—
3.722% Secured Tower Revenue Securities Series 2013-2C		542,254		575,000		575,000		—		—		—
3.598% Secured Tower Revenue Securities Series 2013-1D		319,285		330,000		330,000		—		—		—
Revolving Credit Facility		—		—		—		100,000		100,000		100,000
2011 Term Loan B		180,529		180,529		180,201		493,731		492,500		491,518
2012-1 Term Loan A		190,238		190,000		190,000		194,513		195,000		195,000
2012-2 Term Loan B		109,971		109,971		109,725		300,750		300,000		299,278
Total debt	$	6,444,851	$	5,694,223	$	5,641,209	$	6,478,465	$	5,440,073	$	5,356,103