Other Comprehensive Income - Schedule of Changes in Accumulated Other Comprehensive Loss after Tax (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	$ (50,909)
Total other comprehensive income (loss)	12,657	11,532	(56,722)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(38,252)	(50,909)
Unrealized Gains and Losses on AFS Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	906	(3,231)	14,930
Other comprehensive income (loss) before reclassifications	(13,239)	5,682	1,513
Amounts reclassified from other comprehensive income (loss)	(8,522)	(1,545)	(19,674)
Total other comprehensive income (loss)	(21,761)	4,137	(18,161)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(20,855)	906	(3,231)
Non-Credit Impairment Losses on Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(4,175)	(16,566)	(1,543)
Other comprehensive income (loss) before reclassifications	3,637	9,942	(26,656)
Amounts reclassified from other comprehensive income (loss)	(268)	2,449	11,633
Total other comprehensive income (loss)	3,369	12,391	(15,023)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(806)	(4,175)	(16,566)
Unrealized Gains and Losses on Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(12,676)	(13,085)	(708)
Other comprehensive income (loss) before reclassifications	2,400	(3,351)	(14,157)
Amounts reclassified from other comprehensive income (loss)	4,005	3,760	1,780
Total other comprehensive income (loss)	6,405	409	(12,377)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(6,271)	(12,676)	(13,085)
Defined Benefit Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(34,964)	(29,559)	(18,398)
Other comprehensive income (loss) before reclassifications	21,577	(6,839)	(12,404)
Amounts reclassified from other comprehensive income (loss)	3,067	1,434	1,243
Total other comprehensive income (loss)	24,644	(5,405)	(11,161)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(10,320)	(34,964)	(29,559)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(50,909)	(62,441)	(5,719)
Other comprehensive income (loss) before reclassifications	14,375	5,434	(51,704)
Amounts reclassified from other comprehensive income (loss)	(1,718)	6,098	(5,018)
Total other comprehensive income (loss)	12,657	11,532	(56,722)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	$ (38,252)	$ (50,909)	$ (62,441)