Derivative Financial Instruments - Summary of Notional Values and Fair Values of Derivative Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivative Liabilities
Fair Value	$ (3,634)	$ (2,705)
Cash Flow Hedging | Designated as Hedging Instrument | Interest Rate Swap
Derivative Liabilities
Notional Amount	210,000
Fair Value	(3,634)
Cash Flow Hedging | Designated as Hedging Instrument | Unsecured term loan facility with: 1.2175 % Swap Rate, Expiration Date 04/2016
Derivative Liabilities
Notional Amount	75,000
Fixed rate	1.2175%
Fair Value	(693)
Cash Flow Hedging | Designated as Hedging Instrument | Unsecured term loan facility with: 2.0480 % Swap Rate, Expiration Date 10/2018
Derivative Liabilities
Notional Amount	30,000
Fixed rate	2.048%
Fair Value	(1,007)
Cash Flow Hedging | Designated as Hedging Instrument | Unsecured term loan facility with: 1.8500 % Swap Rate, Expiration Date 10/2018
Derivative Liabilities
Notional Amount	25,000
Fixed rate	1.85%
Fair Value	(669)
Cash Flow Hedging | Designated as Hedging Instrument | Unsecured term loan facility with: 1.8400 % Swap Rate, Expiration Date 10/2018
Derivative Liabilities
Notional Amount	5,000
Fixed rate	1.84%
Fair Value	(132)
Cash Flow Hedging | Designated as Hedging Instrument | Unsecured term loan facility with: 2.1500 % Swap Rate, Expiration Date 05/2020
Derivative Liabilities
Notional Amount	15,000
Fixed rate	2.15%
Fair Value	(572)
Cash Flow Hedging | Designated as Hedging Instrument | Unsecured term loan facility with: 2.1500 % Swap Rate, Expiration Date 05/2020
Derivative Liabilities
Notional Amount	10,000
Fixed rate	2.15%
Fair Value	(382)
Cash Flow Hedging | Designated as Hedging Instrument | Unsecured term loan facility with: 1.4600 % Swap Rate, Expiration Date 05/2020
Derivative Liabilities
Notional Amount	50,000
Fixed rate	1.46%
Fair Value	$ (179)