Derivative Instruments and Hedging Activities - Summary of Offsetting of Financial Liabilities and Derivative Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Offsetting Assets [Line Items]
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	$ 16,951	$ 9,716
Interest Rate Swaps
Offsetting Assets [Line Items]
Gross Amount of Recognized Liabilities	16,951	9,703
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	16,951	9,703
Gross amounts not offset in the consolidated balance sheet, Financial instruments	0	192
Gross amounts not offset in the consolidated balance sheet, Cash collateral pledged	16,951	9,511
Gross amounts not offset in the consolidated balance sheet, Net amount	$ 0	$ 0