Cash and Cash Equivalents, Short-term Investments and Fair Value of Financial Instruments marketable securities - gain or loss (Details) (USD $)	53 Months Ended
	Jun. 30, 2012	Sep. 30, 2012	Dec. 31, 2011		Sep. 30, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Money Market Fund - daily traded value	$ 1.00
Cash and cash equivalents, Amortized Cost		54,818,000	191,762,000	[1]	179,303,000	175,635,000
Cash, cash equiv and S-T-I: Amortized cost		54,818,000	199,868,000
Cash, cash equiv and S-T-I: Gross unrealized gains		0	1,000
Cash, cash equiv and S-T-I: Gross unrealized losses		0	0
Cash, Cash Equivalents, and Short-term Investments		54,818,000	199,869,000
Cash [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents, Amortized Cost		22,911,000	14,452,000
Cash and cash equivalents - gross unrealized gain		0	0
Cash and cash equivalents - Gross unrealized losses		0	0
Cash and Cash Equivalents, Fair Value Disclosure		22,911,000	14,452,000
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents, Amortized Cost		31,907,000	177,310,000
Cash and cash equivalents - gross unrealized gain		0	0
Cash and cash equivalents - Gross unrealized losses		0	0
Cash and Cash Equivalents, Fair Value Disclosure		31,907,000	177,310,000
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
A-F-S Securities, Amortized Cost Basis			8,106,000
A-F-S Securities, Gross Unrealized Gains			1,000
A-F-S Securities, Gross Unrealized Losses			0
A-F-S, Fair Value Disclosure			8,107,000
Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, Cash Equivalents, and Short-term Investments		54,818,000	191,762,000
Cash and Cash Equivalents [Member] | Cash [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		22,911,000	14,452,000
Cash and Cash Equivalents [Member] | Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		31,907,000	177,310,000
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash, Cash Equivalents, and Short-term Investments		0	8,107,000
Short-term Investments [Member] | US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
A-F-S, Fair Value Disclosure			$ 8,107,000

[1] Information derived from our December 31, 2011 audited Consolidated Financial Statements.