Subsequent Events (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Subsequent Event [Line Items]
Stock Issued During Period, Shares, Conversion of Convertible Securities	4,487,060
Common shares issued	178,616,664	154,938,351
Proceeds from issuance of common shares	$ 162,747,000	$ 99,730,000	$ 166,652,000
Settlement of Debt [Member]
Subsequent Event [Line Items]
Stock Issued During Period, Shares, Conversion of Convertible Securities	5,049,096
Refinancing of Debt [Member]
Subsequent Event [Line Items]
Debt Instrument, Amount Amended	255,000,000
Suwanee, Georgia [Member] | Settlement of Debt [Member]
Subsequent Event [Line Items]
Debt conversion, original debt, amount	10,964,000
Six Percent Convertible Guaranteed Note [Member]
Subsequent Event [Line Items]
Debt conversion, original debt, amount	31,104,000
Debt Conversion, Converted Instrument, Amount	31,104,000
Debt Conversion, Converted Instrument, Cash Payment During Conversion	2,427,000
Debt instrument amount	83,896,000		115,000,000
Six Percent Convertible Guaranteed Note [Member] | Settlement of Debt [Member]
Subsequent Event [Line Items]
Debt Conversion, Converted Instrument, Amount	35,000,000
Debt Conversion, Converted Instrument, Cash Payment During Conversion	2,275,000
Secured Revolving Credit Facility [Member] | Refinancing of Debt [Member]
Subsequent Event [Line Items]
Line of Credit Facility, Amount Refinanced	300,000,000
Unsecured Term Loan [Member] | Refinancing of Debt [Member]
Subsequent Event [Line Items]
Debt instrument amount	250,000,000
Debt Instrument, Term	5 years
Unsecured Revolving Credit Facility, Expiring February 2017 [Member] | Refinancing of Debt [Member]
Subsequent Event [Line Items]
Debt instrument amount	300,000,000
Minimum [Member] | Unsecured Term Loan [Member] | Refinancing of Debt [Member]
Subsequent Event [Line Items]
Basis spread on variable rate	1.45%
Minimum [Member] | Unsecured Revolving Credit Facility, Expiring February 2017 [Member] | Refinancing of Debt [Member]
Subsequent Event [Line Items]
Basis spread on variable rate	1.50%
Maximum [Member] | Unsecured Term Loan [Member] | Refinancing of Debt [Member]
Subsequent Event [Line Items]
Basis spread on variable rate	2.00%
Maximum [Member] | Unsecured Revolving Credit Facility, Expiring February 2017 [Member] | Refinancing of Debt [Member]
Subsequent Event [Line Items]
Basis spread on variable rate	2.05%
At The Market [Member] | Issuance of Equity [Member]
Subsequent Event [Line Items]
Common shares, authorized shares (in shares)	100,000,000
Common shares issued	3,409,927
Proceeds from issuance of common shares	$ 36,884,000