Accumulated Other Comprehensive Income (Loss) Reclassifications Out of AOCI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (11,577)	$ 42,991	$ (24,244)	$ 48,603
Other comprehensive income (loss) before reclassification	35,557	(111,829)	56,184	(121,760)
Amounts reclassified from accumulated other comprehensive income (loss)	297	1,056	250	1,846
Income tax (expense) benefit	(13,783)	42,767	(21,696)	46,296
Total other comprehensive income (loss)	22,071	(68,006)	34,738	(73,618)
Ending Balance	10,494	(25,015)	10,494	(25,015)
Securities Available For Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	1,067	79,828	(11,396)	86,109
Other comprehensive income (loss) before reclassification	35,557	(111,829)	56,184	(121,760)
Amounts reclassified from accumulated other comprehensive income (loss)	(34)	(34)	(412)	(334)
Income tax (expense) benefit	(13,655)	43,188	(21,441)	47,138
Total other comprehensive income (loss)	21,868	(68,675)	34,331	(74,956)
Ending Balance	22,935	11,153	22,935	11,153
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(12,644)	(36,837)	(12,848)	(37,506)
Other comprehensive income (loss) before reclassification	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	331	1,090	662	2,180
Income tax (expense) benefit	(128)	(421)	(255)	(842)
Total other comprehensive income (loss)	203	669	407	1,338
Ending Balance	$ (12,441)	$ (36,168)	$ (12,441)	$ (36,168)