Derivatives - Offsetting Derivative Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross Amounts Recognized	$ 15,129	$ 13,779
Gross Amounts Offset in the Statement of Financial Position
Net Amounts Presented in the Statement of Financial Position	15,129	13,779
Gross Amounts Not Offset in the Statement of Financial Position - Financial Instruments	2,206	3,462
Gross Amounts Not offset in the Statement of Financial Position -Cash Collateral	16,767	7,406
Net Amount	(3,844)	2,911
Gross Amounts Recognized	14,690	14,149
Gross Amounts Offset in the Statement of Financial Position
Net Amounts Presented in the Statement of Financial Position	14,690	14,149
Gross Amounts Not Offset in the Statement of Financial Position - Financial Instruments	2,206	3,462
Gross Amounts Not offset in the Statement of Financial Position -Cash Collateral
Net Amount	$ 12,484	$ 10,687