| Real Estate and Intangible Assets - Weighted Average Amortization Period for Intangible Assets Acquired and Liabilities Assumed (Detail) | 9 Months Ended | |
|---|---|---|
| Sep. 30, 2013 | Sep. 30, 2012 | |
| Acquired Finite-Lived Intangible Assets [Line Items] | ||
| All intangible assets and liabilities | 12 years 8 months 12 days | 3 years 2 months 12 days | 
| In-Place Leases [Member] | ||
| Acquired Finite-Lived Intangible Assets [Line Items] | ||
| All intangible assets and liabilities | 3 years 1 month 6 days | |
| Leasing Commissions [Member] | ||
| Acquired Finite-Lived Intangible Assets [Line Items] | ||
| All intangible assets and liabilities | 12 years 8 months 12 days | 4 years 8 months 12 days | 
| Customer Relationships [Member] | ||
| Acquired Finite-Lived Intangible Assets [Line Items] | ||
| All intangible assets and liabilities | 5 years 9 months 18 days | |
| Below-Market Leases [Member] | ||
| Acquired Finite-Lived Intangible Assets [Line Items] | ||
| All intangible assets and liabilities | 9 months 18 days | |