Computing Basic and Diluted Earnings Per Common Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator for earnings per common share-basic:
Net income	$ 12,035	$ 10,067	$ 31,951	$ 12,031
Net income allocable to noncontrolling interests - operating partnership	(2,344)	(2,446)	(6,662)	(3,236)
Numerator for earnings per common share/unit - basic	9,691	7,621	25,289	8,795
Numerator for earnings per common share/unit - diluted:
Numerator for earnings per common share/unit - basic	9,691	7,621	25,289	8,795
Net income allocable to noncontrolling interests-OP units	2,344	2,446	6,662	2,228
Numerator for earnings per common share/unit - diluted	$ 12,035	$ 10,067	$ 31,951	$ 11,023
Denominator for earnings per common share/unit - basic and diluted:
Denominator for earnings per common share/unit - basic	47,213,612	37,271,714	43,576,705	32,408,843
Effect of dilutive securities:
Noncontrolling interests-OP units	11,419,777	11,938,420	11,478,543	8,221,330
Denominator for earnings per common share/unit - diluted	60,967,867	50,838,529	57,127,784	42,101,077
Basic earnings per share/unit:
Net income allocable to common stockholders	$ 0.21	$ 0.20	$ 0.58	$ 0.27
Diluted earnings per share/unit:
Net income allocable to common stockholders	$ 0.20	$ 0.20	$ 0.56	$ 0.26
Stock Option
Effect of dilutive securities:
Incremental to dilutive securities	2,155,075	1,599,302	1,953,632	1,454,735
Restricted Stock Units (RSUs)
Effect of dilutive securities:
Incremental to dilutive securities	179,403	29,093	118,904	16,169