Earnings Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Earnings Per Share Disclosure [Line Items]
net income attributable to noncontrolling interest, excluding from EPS due to antidilution	$ 0	[1]
Shares Outstanding
Weighted average common shares - basic	39,505		35,706
Weighted average partnership units outstanding	0		2,101
Effect of dilutive securities	102		97
Weighted average common shares - diluted	39,607		37,904
Calculation of Earnings per Share - basic
Net income available for common shareholders	23,890		8,844
Net income allocated to unvested restricted shares	(28)		(9)
Net income available for common shareholders, adjusted	23,862		8,835
Weighted average common shares - basic	39,505		35,706
Earnings per share - basic	$ 0.60		$ 0.25
Calculation of Earnings per Share - diluted
Net income available for common shareholders	23,890		8,844
Net income attributable to noncontrolling interests	1,178		311
Adjusted net income available for common shareholders	$ 23,890		$ 9,155
Weighted average common shares - diluted	39,607		37,904
Earnings per share - diluted	$ 0.60		$ 0.24

[1] Operating partnership units are not included in dilutive earnings per share calculations for the three months ended March 31, 2012, as they were not dilutive.