Income Taxes (Components of the Net Deferred Tax Asset and Related Valuation Allowance) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Income Taxes
Allowances, accruals and other items not currently deductible	$ 31,561	$ 17,673
Net operating loss carryforwards	0	16,279
Current deferred liabilities	(2,509)	(17,345)
Subtotal	29,052	16,607
Less: Valuation allowance	(3,298)	(517)
Net short-term deferred tax assets	25,754	16,090
Net operating loss carryforwards	127,914	48,962
Accrued asset retirement obligations	70,797	50,131
Stock-based compensation	25,258	26,993
Deferred revenue	21,912	20,896
Items not currently deductible and other	55,924	27,396
Depreciation and amortization	(42,896)	31,264
Deferred rent	(18,640)	(9,987)
Other	(4,566)	(2,031)
Subtotal	235,703	193,624
Valuation Allowance	(92,260)	(5,321)
Net long-term deferred tax (liabilities) assets	$ 143,443	$ 188,303