Comprehensive Income - Accumulated Other Comprehensive Income (Loss), Net Consisted of Unrealized Gains (Losses) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (64,159)	$ (240,264)
Net gain (loss) during period	38,898	14,311
Ending Balance	(25,261)	(225,953)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(98,182)
Net gain (loss) during period	820
Ending Balance	(97,362)
Accumulated Other Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	97
Net gain (loss) during period	(136)
Ending Balance	(39)
Investment Securities [Member] | Investment Securities With OTTI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	22,632
Net gain (loss) during period	12,132
Ending Balance	34,764
Investment Securities [Member] | Investment Securities All Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	11,294
Net gain (loss) during period	26,082
Ending Balance	$ 37,376