Derivatives - Offsetting Derivative Assets and Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross Amounts Recognized, Derivative Liabilities	$ 18,338	$ 18,627
Gross Amounts Offset in the Statement of Financial Position, Derivative Liabilities	0	0
Net Amounts Presented in the Statement of Financial Position, Derivative Liabilities	18,338	18,627
Gross Amounts Not Offset in the Statement of Financial Position - Financial Instruments, Derivative Liabilities	474	936
Gross Amounts Not offset in the Statement of Financial Position -Cash Collateral, Derivative Liabilities	20,121	17,343
Net Amount, Derivative Liabilities	(2,257)	348
Gross Amounts Recognized, Derivative Assets	17,998	17,931
Gross Amounts Offset in the Statement of Financial Position, Derivative Assets	0	0
Net Amounts Presented in the Statement of Financial Position, Derivative Assets	17,998	17,931
Gross Amounts Not Offset in the Statement of Financial Position - Financial Instruments, Derivative Assets	474	936
Gross Amounts Not offset in the Statement of Financial Position -Cash Collateral, Derivative Assets	0	0
Net Amount, Derivative Assets	$ 17,524	$ 16,995