Concentrations - Geographic Revenue Concentrations from Consolidated Properties (Detail)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	95.85%	95.27%
Percentage of geographic revenue concentrations from consolidated properties	100.00%	100.00%
New Jersey [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	28.41%	26.67%
Virginia [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	10.93%	13.70%
California [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	8.93%	11.23%
South Carolina [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	8.48%	8.86%
Texas [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	8.38%	8.85%
Massachusetts [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	5.78%	6.85%
Florida [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	5.45%	5.20%
Illinois [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	4.37%	2.84%
Arizona [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	4.18%	0.75%
Minnesota [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	3.53%	4.59%
North Carolina [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	2.62%	2.26%
Colorado [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	1.46%	0.00%
Georgia [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	1.25%	1.52%
Kentucky [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	0.82%	1.03%
Utah [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	0.75%	0.92%
Kansas [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of domestic geographic revenue concentrations from consolidated properties	0.51%	0.00%
United Kingdom [Member]
Information About Revenue And Geographic Areas [Line Items]
Percentage of international geographic revenue concentrations from consolidated properties	4.15%	4.73%