Long-Term Debt (Senior Notes) (Details) (USD $)	0 Months Ended	12 Months Ended			0 Months Ended				0 Months Ended	12 Months Ended
	Oct. 14, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Apr. 12, 2010 5.75% Notes, Payable January 15, 2011 [Member]	Jan. 15, 2006 5.75% Notes, Payable January 15, 2011 [Member]	Dec. 31, 2011 5.75% Notes, Payable January 15, 2011 [Member]	Oct. 14, 2010 5.75% Notes, Payable January 15, 2011 [Member]	Jan. 15, 2006 6.125% Notes, Payable January 15, 2016 [Member]	Dec. 31, 2011 6.125% Notes, Payable January 15, 2016 [Member]	Dec. 31, 2011 7.20% Senior Notes, Payable April 15, 2012 [Member]
Debt Instrument [Line Items]
Notes payable, maturity date					Jan. 15, 2011	Jan. 15, 2016				Jan. 15, 2016	Apr. 15, 2012
Interest rate percentage					5.75%	5.75%	5.75%			6.125%	7.20%
Aggregate principal amount of debts					$ 200,000,000	$ 500,000,000				$ 900,000,000	$ 400,000,000
Senior notes principal amount percentage					103.50%
Senior notes premium and fees					514,000
Restricted account cash deposits								27,942,000
Senior notes premium to note holders					7,000,000
Debt reserves								280,000
Repayment of debt including interest	170,000,000
Notes borrowings	138,000,000
Remaining outstanding senior notes repaid											63,730,000
Increase in interest rate from rating agency downgrade									0.25%
Maximum increase in interest rate per agency from rating agency downgrade									1.00%	1.00%
Increase in interest expense per quarter for .25% increase in notes per $100,000 of outstanding notes		101,617,000	133,151,000	127,031,000					63	63
Incremental increase in outstanding notes									$ 100,000	$ 100,000
Aggregate amount of increase in interest rate from rating agency downgrade									0.75%	0.75%
Repurchase price as percentage of principal amount of senior notes											102.72%