Derivative Instruments and Hedging Activities - Summary of Offsetting of Financial Assets and Derivative Assets (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Offsetting Assets [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet	$ 8,810	$ 7,552
Interest Rate Swaps
Offsetting Assets [Line Items]
Gross Amount of Recognized Assets	208	192
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	208	192
Gross amounts not offset in the consolidated balance sheet, Financial instruments	208	192
Gross amounts not offset in the consolidated balance sheet, Cash collateral received	0	0
Gross amounts not offset in the consolidated balance sheet, Net amount	$ 0	$ 0