Borrowings (Narrative) (Details) (USD $)	12 Months Ended				3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Nov. 22, 2011	Dec. 31, 2011 Institutional And Accredited Investor [Member]	Dec. 31, 2011 Institutional And Accredited Investor [Member]
Debt Instrument [Line Items]
Initial conversion rate	$ 21.46
Carrying amount of the equity component recognized upon adoption	$ 17,770,000			$ 18,210,000
Unamortized debt issuance costs	440,000
Discount on convertible notes	3,040,000
Original issue discount	98.00%
Interest expense	2,090,000	587,000	618,000
Interest income	51,000	32,000	9,000
Interest rate	5.50%
Private placement of senior convertible notes	152,000,000				152,000,000	152,000,000
Issuance costs					6,634,000
Proceeds from issuance of notes	148,960,000				145,366,000	145,366,000
Amortization of debt discount	409,000
Converted number of common stock shares	46.6021
Debt instrument periodic payment of interest	payable in cash semi-annually on June 15 and December 15 of each year
Convertible Senior Notes principal amount	1
Shares of common stock that are convertible	7,084,000
Notes issued with an effective yield	5.96%
Recognized deferred tax liability tax effect	$ 7,200,000
Redeemable convertible securities maximum, shares	9,031,000
Redeemable convertible securities price per share	$ 16.83