Borrowings (Convertible Senior Notes Due 2013) (Details) (Convertible Senior Notes Due 2013 [Member], USD $)	0 Months Ended	3 Months Ended
	Mar. 07, 2008	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Convertible Senior Notes Due 2013 [Member]
Debt Instrument [Line Items]
Debt instrument issuance amount	$ 310,000,000
Interest rate percentage on issued debt	3.00%
Year of maturity of debt	2013
Initial conversion rate shares	14.7113
Principal amount of initial conversion rate	1,000
Accrued interest		400,000		2,700,000
Pre tax non-cash interest expense recognized in consolidated statement of operations		1,100,000	1,100,000
Annual pre-tax increase in non-cash interest expense		3,200,000
Accumulated amortization related to debt discount		$ 16,500,000	$ 12,200,000