Debt - Summary of Debt (Parenthetical) (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Fixed-Rate Mortgage Notes [Member]
Debt Instrument [Line Items]
Interest rate range, minimum	3.30%
Interest rate range, maximum	6.24%
Secured Line of Credit [Member]
Debt Instrument [Line Items]
Unused portion of line of credit	$ 55,000,000
Amount available under line of credit	36,900,000
Unsecured Line of Credit [Member]
Debt Instrument [Line Items]
Unused portion of line of credit	277,000,000
Amount available under line of credit	75,500,000
$200 Million Term Loan Interest Rate Swap [Member]
Debt Instrument [Line Items]
Notional amount	$ 200,000,000
Effective date of interest rate swap agreement	Jan. 14, 2014
All-in interest rate	2.68%
Variable-Rate Mortgage Note [Member]
Debt Instrument [Line Items]
Interest rate spread based on LIBOR	2.00%
Minimum [Member] | Secured Line of Credit [Member]
Debt Instrument [Line Items]
Interest rate spread based on LIBOR	1.80%
Minimum [Member] | Unsecured Line of Credit [Member]
Debt Instrument [Line Items]
Interest rate spread based on LIBOR	1.75%
Minimum [Member] | Unsecured Term Loans [Member]
Debt Instrument [Line Items]
Interest rate spread based on LIBOR	1.50%
Maximum [Member] | Secured Line of Credit [Member]
Debt Instrument [Line Items]
Interest rate spread based on LIBOR	2.65%
Maximum [Member] | Unsecured Line of Credit [Member]
Debt Instrument [Line Items]
Interest rate spread based on LIBOR	2.50%
Maximum [Member] | Unsecured Term Loans [Member]
Debt Instrument [Line Items]
Interest rate spread based on LIBOR	2.45%