Debt 3.75% Senior Exchangeable Notes issued October 2007 (Details) (USD $)	1 Months Ended	6 Months Ended	12 Months Ended	1 Months Ended
	Oct. 31, 2007 Warrants on Senior Exchangeable Notes due 2012 [Member]	Jun. 30, 2013 Warrants on Senior Exchangeable Notes due 2012 [Member] unit	Dec. 31, 2013 Warrants on Senior Exchangeable Notes due 2012 [Member]	Oct. 31, 2012 Senior Exchangeable Notes due 2012 at a fixed interest rate of 3.75% [Member]	Oct. 31, 2007 Senior Exchangeable Notes due 2012 at a fixed interest rate of 3.75% [Member]	Dec. 31, 2013 Senior Exchangeable Notes due 2012 at a fixed interest rate of 3.75% [Member]	Oct. 31, 2007 Senior Exchangeable Notes Due 2012 at a fixed interest rate of 3.75% [Member]
Debt Instrument [Line Items]
Issuance date of debt instrument					October 2007
Face amount					$ 300,000,000
Fixed interest rate					3.75%	3.75%	3.75%
Option indexed to issuer's equity, indexed shares					8,239,920
Maturity date description					October 2012
Redemption amount settled				$ 300,000,000
Option indexed to issuer's equity, shares paid					2,221,056
Beginning date for maturity of warrants	Jan. 15, 2013		Jan. 15, 2013
Ending date for maturity of warrants	Mar. 27, 2013		Mar. 27, 2013
Total number of warrants		8,313,511
Settlement of warrants (in shares)		2,135,221	2,135,221