Long-Term Incentive Plan Units (Narrative) (Details) (USD $)	12 Months Ended			64 Months Ended		0 Months Ended	4 Months Ended	64 Months Ended	0 Months Ended	64 Months Ended	12 Months Ended			64 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012	Dec. 31, 2012 Directors [Member] Long-Term Incentive Plan Units [Member]	Sep. 12, 2012 Independent Directors [Member] Long-Term Incentive Plan Units [Member]	Dec. 31, 2007 Manager [Member] Long-Term Incentive Plan Units [Member]	Dec. 31, 2012 Manager [Member] Long-Term Incentive Plan Units [Member]	Dec. 12, 2012 Dedicated Personnel [Member] Long-Term Incentive Plan Units [Member]	Dec. 31, 2012 Dedicated Personnel [Member] Long-Term Incentive Plan Units [Member]	Dec. 31, 2012 Non-Manager [Member] Long-Term Incentive Plan Units [Member]	Dec. 31, 2011 Non-Manager [Member] Long-Term Incentive Plan Units [Member]	Dec. 31, 2010 Non-Manager [Member] Long-Term Incentive Plan Units [Member]	Dec. 31, 2012 Non-Manager [Member] Long-Term Incentive Plan Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
LTIP units granted					24,096	5,346	375,000		2,500	8,000
Aggregate expense associated with Manager LTIP, Since inception								$ 8,600,000
Vesting period											1 year
Allocated Share-based Compensation Expense	135,000	147,000	1,987,000								140,000	150,000	100,000	500,000
Common shares issued in connection with conversion since inception				10,000
Amount transferred from share-based LTIP awards to Shareholders Equity				$ 200,000
Common shares issued and outstanding	20,767,565	16,838,151	16,883,342	20,767,565
Shareholders' equity per share upon conversion (in usd per share)	$ 24.38	$ 22.03	$ 23.91	$ 24.38