Derivative Instruments and Hedging Activities - Summary of Offsetting of Financial Assets and Derivative Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Offsetting Assets [Line Items]
Net amounts of assets presented in the consolidated balance sheet	$ 7,552	$ 3,763
Interest Rate Swaps
Offsetting Assets [Line Items]
Gross amount of recognized assets	192	392
Gross amounts offset in the consolidated balance sheet	0	0
Net amounts of assets presented in the consolidated balance sheet	192	392
Gross amounts not offset in the consolidated balance sheet, Financial instruments	192	392
Gross amounts not offset in the consolidated balance sheet, Cash collateral received	0	0
Net amount	$ 0	$ 0