Summary of Distributions Accrued in Accordance with Declaration to Partnership's Partners (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Distribution Made to Limited Partner [Line Items]
Distributions to the Partnership's partners			$ 12,374
Operating Partnership Units
Distribution Made to Limited Partner [Line Items]
Distributions to the Partnership's partners	4,110	4,298	12,374	8,882
Common Stock
Distribution Made to Limited Partner [Line Items]
Distributions to the Partnership's partners	17,009	13,435	47,666	34,286
Class A
Distribution Made to Limited Partner [Line Items]
Distributions to the Partnership's partners				2,797
Class B
Distribution Made to Limited Partner [Line Items]
Distributions to the Partnership's partners				97
Class C
Distribution Made to Limited Partner [Line Items]
Distributions to the Partnership's partners				146
Class F
Distribution Made to Limited Partner [Line Items]
Distributions to the Partnership's partners				$ 554