Comprehensive Income - Accumulated Other Comprehensive Income (Loss), Net Consisted of Unrealized Gains (Losses) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			$ (240,264)	$ (356,441)
Net gain (loss) during period	(1,818)	53,409	12,493	78,592
Ending Balance	(227,771)	(277,849)	(227,771)	(277,849)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(276,771)
Net gain (loss) during period			10,182
Ending Balance	(266,589)		(266,589)
Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(284)
Net gain (loss) during period			(1,046)
Ending Balance	(1,330)		(1,330)
Investment Securities [Member] | Investment Securities With OTTI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(55,790)
Net gain (loss) during period			64,759
Ending Balance	8,969		8,969
Investment Securities [Member] | Investment Securities All Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			92,581
Net gain (loss) during period			(61,402)
Ending Balance	$ 31,179		$ 31,179