Basis Of Presentation (Details) (USD $)	1 Months Ended	9 Months Ended
	Feb. 28, 2011	Sep. 30, 2011
Basis Of Presentation [Line Items]
Principal amount		$ 1,000
Convertible senior notes, interest rate		4.75%
Convertible senior notes, maturity date		Feb. 01, 2018
Deferred finance costs		4,900,000
Deferred finance costs recorded as a long-term asset		4,246,000
Deferred financing costs amortization period		7
Debt Component [Member]
Basis Of Presentation [Line Items]
Financing costs		5,400,000
Equity Component [Member]
Basis Of Presentation [Line Items]
Financing costs		1,900,000
4.75% Convertible Senior Notes Due On 2018 [Member]
Basis Of Presentation [Line Items]
Financing costs		7,300,000
Principal amount	$ 230,000,000	$ 230,000,000
Convertible senior notes, interest rate		4.75%
Convertible senior notes, maturity date	Feb. 01, 2018	Feb. 01, 2018