Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income, Net of Tax) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 238,048	$ 247,734	$ 154,250
Other comprehensive income (loss) before reclassification	(75,195)	14,669	119,099
Amounts reclassified from accumulated other comprehensive income (loss)	(22,419)	(24,355)	(25,615)
Net other comprehensive income (loss) during period	(97,614)	(9,686)	93,484
Ending Balance	140,434	238,048	247,734
Securities Available For Sale [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	245,539	227,052	96,012
Other comprehensive income (loss) before reclassification	(98,103)	21,291	135,209
Amounts reclassified from accumulated other comprehensive income (loss)	(764)	(2,804)	(4,169)
Net other comprehensive income (loss) during period	(98,867)	18,487	131,040
Ending Balance	146,672	245,539	227,052
Defined Benefit Plans [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(49,071)	(42,958)	(28,357)
Other comprehensive income (loss) before reclassification	22,940	(6,113)	(14,601)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0
Net other comprehensive income (loss) during period	22,940	(6,113)	(14,601)
Ending Balance	(26,131)	(49,071)	(42,958)
Derivatives [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	41,580	63,640	86,595
Other comprehensive income (loss) before reclassification	(32)	(509)	(1,509)
Amounts reclassified from accumulated other comprehensive income (loss)	(21,655)	(21,551)	(21,446)
Net other comprehensive income (loss) during period	(21,687)	(22,060)	(22,955)
Ending Balance	$ 19,893	$ 41,580	$ 63,640