Change in Accumulated Other Comprehensive Income (Loss) - Components of Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains on securities transactions	$ 15,600	$ 15,053
Income taxes	1,311	(5,313)
Net Unrealized (Losses) Gains on Investment Securities Available-for-Sale [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized gains on securities transactions	578	1,644
Income taxes	(220)	(625)
Net of tax	$ 358	$ 1,019