Fair Value Of Financial Instruments (Condensed Consolidated Balance Sheet Presentation Of Financial Instruments Measured And Recorded At Fair Value On A Recurring Basis, Excluding Accrued Interest Components) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities fair value disclosure recurring	$ 691
Assets fair value disclosure recurring	957,595		710,407
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities fair value disclosure recurring	0
Assets fair value disclosure recurring	536,326		236,533
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities fair value disclosure recurring	213
Assets fair value disclosure recurring	368,678		405,229
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities fair value disclosure recurring	478
Assets fair value disclosure recurring	52,591		68,645
Cash And Cash Equivalents [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	454,208		172,181
Cash And Cash Equivalents [Member] | Money Market Funds [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	454,208		172,181
Cash And Cash Equivalents [Member] | Money Market Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0		0
Cash And Cash Equivalents [Member] | Money Market Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0		0
Short-Term Investments [Member] | Municipal Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	262,793		291,296
Short-Term Investments [Member] | Municipal Bonds [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0		0
Short-Term Investments [Member] | Municipal Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	262,793		291,296
Short-Term Investments [Member] | Municipal Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0		0
Short-Term Investments [Member] | Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	49,008		18,966
Short-Term Investments [Member] | Corporate Bonds [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0		0
Short-Term Investments [Member] | Corporate Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	49,008		18,966
Short-Term Investments [Member] | Corporate Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0		0
Short-Term Investments [Member] | Variable Rate Demand Notes [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	56,540		94,849
Short-Term Investments [Member] | Variable Rate Demand Notes [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0		0
Short-Term Investments [Member] | Variable Rate Demand Notes [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	56,540		94,849
Short-Term Investments [Member] | Variable Rate Demand Notes [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0		0
Short-Term Investments [Member] | Auction Rate Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	9,700
Short-Term Investments [Member] | Auction Rate Securities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0
Short-Term Investments [Member] | Auction Rate Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0
Short-Term Investments [Member] | Auction Rate Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	9,700
Other Current Assets [Member] | Derivative Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	337	[1]	118	[1]
Other Current Assets [Member] | Derivative Assets [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0	[1]	0	[1]
Other Current Assets [Member] | Derivative Assets [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	337	[1]	118	[1]
Other Current Assets [Member] | Derivative Assets [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0	[1]	0	[1]
Non-Current Restricted Cash And Cash Equivalents [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	82,118		64,352
Non-Current Restricted Cash And Cash Equivalents [Member] | Money Market Funds [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	82,118		64,352
Non-Current Restricted Cash And Cash Equivalents [Member] | Money Market Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0		0
Non-Current Restricted Cash And Cash Equivalents [Member] | Money Market Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0		0
Long-Term Investments [Member] | Auction Rate Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	42,891		68,645
Long-Term Investments [Member] | Auction Rate Securities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0		0
Long-Term Investments [Member] | Auction Rate Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	0		0
Long-Term Investments [Member] | Auction Rate Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Assets fair value disclosure recurring	42,891		68,645
Other Current Liabilities [Member] | Derivative Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities fair value disclosure recurring	213	[1]	1,562	[1]
Other Current Liabilities [Member] | Derivative Liabilities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities fair value disclosure recurring	0	[1]	0	[1]
Other Current Liabilities [Member] | Derivative Liabilities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities fair value disclosure recurring	213	[1]	1,562	[1]
Other Current Liabilities [Member] | Derivative Liabilities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities fair value disclosure recurring	0	[1]	0	[1]
Other Non-Current Liabilities [Member] | Embedded Derivative Liabilities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities fair value disclosure recurring	478	[1]
Other Non-Current Liabilities [Member] | Embedded Derivative Liabilities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities fair value disclosure recurring	0	[1]
Other Non-Current Liabilities [Member] | Embedded Derivative Liabilities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities fair value disclosure recurring	0	[1]
Other Non-Current Liabilities [Member] | Embedded Derivative Liabilities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Liabilities fair value disclosure recurring	$ 478	[1]

[1] See additional disclosures relating to our derivatives and hedging activities in Note 8 below.