Represents the percentage of the closing sales price of the entity's common stock for at least 20 days within 30 consecutive trading days that the closing sales price of the entity's common stock must exceed the applicable conversion price in order for the debt instruments to be redeemable at the reporting entity's option.

No definition available.

Convertible Notes (Details) (USD $)	12 Months Ended			1 Months Ended		3 Months Ended	12 Months Ended			1 Months Ended		12 Months Ended
Convertible Notes (Details) (USD $)	Dec. 31, 2009	Dec. 31, 2011	Dec. 31, 2010	Jul. 31, 2009 5% Convertible Senior Notes due 2014	Jun. 30, 2009 5% Convertible Senior Notes due 2014	Dec. 31, 2009 5% Convertible Senior Notes due 2014	Dec. 31, 2011 5% Convertible Senior Notes due 2014 D Y	Dec. 31, 2010 5% Convertible Senior Notes due 2014	Jun. 29, 2009 5% Convertible Senior Notes due 2014 Y	Feb. 28, 2010 Zero Coupon Convertible Senior Notes due 2010	Feb. 28, 2005 Zero Coupon Convertible Senior Notes due 2010	Dec. 31, 2011 Zero Coupon Convertible Senior Notes due 2010
Convertible Notes
Total principal amount of convertible notes		$ 172,500,000	$ 172,500,000				$ 172,500,000	$ 172,500,000
Unamortized discount		(39,007,000)	(51,000,000)				(39,007,000)	(51,000,000)
Total convertible notes		133,493,000	121,500,000				133,493,000	121,500,000
Total long-term convertible notes		133,493,000	121,500,000
Convertible notes stated interest rate (as a percent)						5.00%	5.00%	5.00%	5.00%
Additional borrowings on debt instrument				22,500,000	150,000,000						300,000,000
Liability component of convertible senior notes principal issued				14,300,000	92,400,000
Equity component of convertible senior notes principal issued				8,200,000	57,600,000
Amortization period of unamortized discount (in years)									5
Periodic interest payment						4,000,000	8,600,000	8,600,000
Issuance cost	4,313,000					5,100,000
Convertible debt issuance costs - liability component						3,200,000
Amortization period of debt issuance costs (in years)							5
Convertible debt issuance costs - equity component						1,900,000
Conversion rate, number of shares to be issued per $1000 of principal (in shares)							51.8					37.2585
Principal amount of notes used as the denominator to determine number of shares converted into notes							1,000					1,000
Initial conversion price of notes (in dollars per share)							$ 19.31					$ 26.84
Number of trading days within 30 consecutive trading days in which the closing price of the entity's common stock must exceed the conversion price for the notes to be redeemable, minimum							20
Number of consecutive trading days during which the closing price of the entity's common stock must exceed the conversion price for at least 20 days in order for the notes to be redeemable							30
Percentage of the closing sales price of the entity's common stock that the conversion price must exceed in order for the notes to be convertible							130.00%
Number of business days immediately after any ten consecutive trading day period during the note measurement period							5
Number of consecutive trading days before the five business days during the debt instrument measurement period							10
Denomination of the principal amount of notes used to calculate the percent of trading price during the debt instrument measurement period							1,000
Maximum conversion price as a percentage of closing stock price							98.00%
Number of trading days conversion reference period							20
Percentage of face amount of debt instrument redeemable at the company's option							100.00%
Number of trading days within 30 consecutive trading days in which the closing price of the entity's common stock must exceed the conversion price for the notes to be redeemable at the company's option, minimum							20
Number of consecutive trading days during which the closing price of the entity's common stock must exceed the conversion price for at least 20 days in order for the notes to be redeemable at the company's option							30
Percentage of the closing sales price of the entity's common stock that the conversion price must exceed in order for the notes to be redeemable at the company's option							130.00%
Percentage of face amount which may be redeemed by the debt holder for cash upon occurrence of a fundamental change							100.00%
Maximum increase in conversion rate per $1000 principal amount upon occurrence of fundamental change							15.5401
Denomination of the principal amount of notes used to calculate the share conversion rate upon occurrence of fundamental change							1,000
Events of default
Period of default in payment of interest (in days)							30
Period of default to comply with other agreements (in days)							60
Minimum percentage of aggregate outstanding principal required for default event with other agreements							25.00%
Minimum principal amount of debt nonpayment required for debt default to occur							30,000,000
Period of nonpayment of principal amount required for debt default to occur (in days)							10
Minimum percentage of aggregate outstanding principal required for nonpayment of debt default to occur							25.00%
Minimum percentage of aggregate outstanding principal required for immediate payment declaration to occur							25.00%
Repayment of debt upon maturity										137,000,000
Equity component of convertible senior notes							$ 63,900,000	$ 63,900,000