Consolidating Financial Statements Text (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			12 Months Ended
	Dec. 31, 2011 Senior Exchangeable Notes due 2012 at a fixed interest rate of 3.75% [Member]	Dec. 31, 2010 Senior Exchangeable Notes due 2012 at a fixed interest rate of 3.75% [Member]	Oct. 01, 2007 Senior Exchangeable Notes due 2012 at a fixed interest rate of 3.75% [Member]	Dec. 31, 2011 Senior Exchangeable Notes due 2015 at a fixed interest rate of 4.50% [Member]	Dec. 31, 2010 Senior Exchangeable Notes due 2015 at a fixed interest rate of 4.50% [Member]	Aug. 01, 2009 Senior Exchangeable Notes due 2015 at a fixed interest rate of 4.50% [Member]
Debt Instrument [Line Items]
Debt Instrument, Issuance Date	October 2007			August 2009
Debt Instrument, Face Amount	$ 300,000	$ 300,000	$ 300,000	$ 172,500	$ 172,500	$ 172,500
Debt Instrument, Interest Rate, Stated Percentage	3.75%		3.75%	4.50%		4.50%
Debt Instrument Scheduled Date of Maturity	2012			2015