Earnings Per Common Share Calculation of numerator and denominator in eps table (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share Disclosure [Line Items]
Net income (loss) available for Common Shares – basic	$ 16,009	$ (2,853)	$ 30,504	$ 22,934
Amounts allocated to dilutive securities	1,503	177	2,891	3,587
Net income (loss) available for Common Shares – fully diluted	$ 17,512	$ (2,676)	$ 33,395	$ 26,521
Weighted average Common Shares outstanding - basic	41,190,000	38,346,000	41,137,000	34,017,000
Redemption of Common OP Units for Common Shares	3,942,000	4,286,000	3,959,000	4,311,000
Incremental Common Shares Attributable to Conversion of Preferred Stock	0	598,000	0	202,000
Employee stock options and restricted shares	315,000	372,000	322,000	328,000
Weighted average Common Shares outstanding - fully diluted	45,447,000	43,602,000	45,418,000	38,858,000
Net income (loss) available for Common Shares	$ 0.39	$ (0.07)	$ 0.74	$ 0.67
Net income (loss) available for Common Shares	$ 0.39	$ (0.07)	$ 0.74	$ 0.67