Debt Senior Notes (Details) (Senior Notes [Member], USD $)	12 Months Ended					12 Months Ended
	Dec. 31, 2010 8.25% Interest Rate [Member]	Dec. 31, 2011 8.25% Interest Rate [Member]	Mar. 31, 2010 8.25% Interest Rate [Member]	Dec. 31, 2011 6.25% Interest Rate [Member]	Dec. 31, 2010 6.25% Interest Rate [Member]	Dec. 31, 2011 Prior to 2015 [Member]	Dec. 31, 2011 Prior to 2018 [Member]
Debt Instrument [Line Items]
Principal	$ 150,000,000	$ 150,000,000	$ 150,000,000	$ 185,000,000	$ 185,000,000
Debt Instrument, Interest Rate, Stated Percentage		8.25%		6.25%
Proceeds from Notes Payable	147,500,000
Business Acquisition, Cost of Acquired Entity, Cash Paid			93,000,000
Line of Credit Facility, Decrease, Repayments	42,000,000
Limit on Prepayment of Senior Notes						$ 206,000,000	$ 171,000,000