Incentive Plan (Summary Of Non-Vested Shares) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012
Incentive Plan [Abstract]
Nonvested at beginning of period, Number of Shares	1,962,171
Granted during period, Number of Shares	932,058
Vested during period, Number of Shares	(621,444)
Forfeited during period, Number of Shares	(29,530)
Nonvested at end of period, Number of Shares	2,243,255
Nonvested at beginning of period, Weighted Average Grant Date Fair Value Per Share	$ 13.41
Granted during period, Weighted Average Grant Date Fair Value Per Share	$ 18.10
Vested during period, Weighted Average Grant Date Fair Value Per Share	$ 13.92
Forfeited during period, Weighted Average Grant Date Fair Value Per Share	$ 16.53
Nonvested at end of period, Weighted Average Grant Date Fair Value Per Share	$ 15.18