Other Comprehensive Income (Schedule of Other Comprehensive Income (Loss)) (Details) (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) [Roll Forward]
Beginning balance	$ (30,911)	$ (46,445)	$ (32,266)	$ (60,204)
Other comprehensive income (loss) before reclassifications	(36,095)	2,391	(36,794)	14,488
Amounts reclassified from accumulated other comprehensive income	1,867	176	3,921	1,838
Net current-period other comprehensive income (loss), net of tax	(34,228)	2,567	(32,873)	16,326
Ending balance	(65,139)	(43,878)	(65,139)	(43,878)
Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(25,961)	(27,843)	(27,902)	(28,884)
Other comprehensive income (loss) before reclassifications	1,581	(1,774)	1,880	(1,681)
Amounts reclassified from accumulated other comprehensive income	1,508	1,221	3,150	2,169
Net current-period other comprehensive income (loss), net of tax	3,089	(553)	5,030	488
Ending balance	(22,872)	(28,396)	(22,872)	(28,396)
Available For Sale and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	41,191	27,625	42,741	15,967
Other comprehensive income (loss) before reclassifications	(38,248)	3,792	(39,730)	15,450
Amounts reclassified from accumulated other comprehensive income	(214)	(1,649)	(282)	(1,649)
Net current-period other comprehensive income (loss), net of tax	(38,462)	2,143	(40,012)	13,801
Ending balance	2,729	29,768	2,729	29,768
Defined Benefit Pension and Postretirement Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(46,141)	(46,227)	(47,105)	(47,287)
Other comprehensive income (loss) before reclassifications	572	373	1,056	719
Amounts reclassified from accumulated other comprehensive income	573	604	1,053	1,318
Net current-period other comprehensive income (loss), net of tax	1,145	977	2,109	2,037
Ending balance	$ (44,996)	$ (45,250)	$ (44,996)	$ (45,250)