Earnings Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011	Jun. 30, 2012		Jun. 30, 2011
Earnings Per Share Disclosure [Line Items]
net income attributable to noncontrolling interest, excluding from EPS due to antidilution	$ 0	[1]		$ 0	[1]
Shares Outstanding
Weighted average common shares - basic	40,983		36,836	40,243		36,274
Weighted average partnership units outstanding	0		1,982	0		2,041
Effect of dilutive securities	45		105	84		105
Weighted average common shares - diluted	41,028		38,923	40,327		38,420
Calculation of Earnings per Share - basic
Net income available for common shareholders	28,160		7,428	52,050		16,272
Net income allocated to unvested restricted shares	(25)		(2)	(54)		(11)
Net income available for common shareholders, adjusted	28,135		7,426	51,996		16,261
Weighted average common shares - basic	40,983		36,836	40,243		36,274
Earnings per share - basic	$ 0.69		$ 0.20	$ 1.29		$ 0.45
Calculation of Earnings per Share - diluted
Net income available for common shareholders	28,160		7,428	52,050		16,272
Net income attributable to noncontrolling interests	1,312		252	2,490		563
Adjusted net income available for common shareholders	$ 28,160		$ 7,680	$ 52,050		$ 16,835
Weighted average common shares - diluted	41,028		38,923	40,327		38,420
Earnings per share - diluted	$ 0.69		$ 0.20	$ 1.29		$ 0.44

[1] Operating partnership units are not included in dilutive earnings per share calculations for the three or six months ended June 30, 2012, as they were not dilutive.