Description of Business (Details)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2011 Segments	Dec. 31, 2010	Dec. 31, 2009
Description of Business [Abstract]
Number of reportable segments	2	2
Percentage of ownership in general partnership	99.55%	99.55%
Percentage of interest in preferred units	100.00%	100.00%
Percentage of common limited partnership interest	0.45%	0.45%
Conversion basis of common stock	0.4464	0.4464	0.4464	0.4464