Other Comprehensive Income (Schedule of Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Available for sale and transferred securities:
Net unrealized loss during the period, Pre-Tax Amount	$ (77,524)	$ 45,024	$ (777)
Net unrealized loss during the period, Tax (Expense) Benefit	27,762	(16,096)	1,527
Net unrealized loss during the period, Net of Tax Amount	(49,762)	28,928	750
Reclassification adjustment for net gain included in net income, Pre-Tax Amount	(712)	(3,347)	(3,823)
Reclassification adjustment for net gain included in net income, Tax (Expense) Benefit	255	1,171	1,338
Reclassification adjustment for net gain included in net income, Net of Tax Amount	(457)	(2,176)	(2,485)
Net non-credit related other-than-temporary impairment, Pre-Tax Amount	7,277	0	0
Net non-credit related other-than-temporary impairment, Tax (Expense) Benefit	(2,606)	0	0
Net non-credit related other-than-temporary impairment, Net of Tax Amount	4,671	0	0
Amortization of unrealized loss on securities transferred to held to maturity, Pre-Tax Amount	296	35	260
Amortization of unrealized loss on securities transferred to held to maturity, Tax (Expense) Benefit	(106)	(13)	(87)
Amortization of unrealized loss on securities transferred to held to maturity, Net of Tax Amount	190	22	173
Total available for sale and transferred securities, Pre-Tax Amount	(70,663)	41,712	(4,340)
Total available for sale and transferred securities, Tax (Expense) Benefit	25,305	(14,938)	2,778
Total available for sale and transferred securities, Net of Tax Amount	(45,358)	26,774	(1,562)
Derivative instruments:
Net unrealized loss during the period, Pre-Tax Amount	5,826	(5,047)	(23,222)
Net unrealized loss during the period, Tax (Expense) Benefit	(2,082)	1,804	8,775
Total derivative instruments, Net of Tax Amount	3,744	(3,243)	(14,447)
Reclassification adjustment for cash flow hedges included in net income, Pre-Tax Amount	9,272	6,575	(13,742)
Reclassification adjustment for cash flow hedges included in net income, Tax (Expense) Benefit	(3,320)	(2,350)	5,194
Reclassification adjustment for cash flow hedges included in net income, Net of Tax Amount	5,952	4,225	(8,548)
Total derivative instruments, Pre-Tax Amount	15,098	1,528	(36,964)
Total derivative instruments, Tax (Expense) Benefit	(5,402)	(546)	13,969
Total derivative instruments, Net of Tax Amount	9,696	982	(22,995)
Defined benefit pension and postretirement benefit plans:
Current year actuarial loss, Pre-Tax Amount	26,949	(3,832)	(35,137)
Current year actuarial loss, Tax (Expense) Benefit	(9,651)	1,370	12,901
Current year actuarial loss, Net of Tax Amount	17,298	(2,462)	(22,236)
Reclassification adjustment for amortization of net loss included in net income, Pre-Tax Amount	3,169	4,042	392
Reclassification adjustment for amortization of net loss included in net income, Tax (Expense) Benefit	(1,135)	(1,445)	(140)
Reclassification adjustment for amortization of net loss included in net income, Net of Tax Amount	2,034	2,597	252
Reclassification adjustment for prior service costs included in net income, Pre-Tax Amount	73	73	73
Reclassification adjustment for prior service costs included in net income, Tax (Expense) Benefit	(26)	(26)	(27)
Reclassification adjustment for prior service costs included in net income, Net of Tax Amount	47	47	46
Total defined benefit pension and postretirement benefit plans, Pre-Tax Amount	30,191	283	(34,672)
Total defined benefit pension and postretirement benefit plans, Tax (Expense) Benefit	(10,812)	(101)	12,734
Total defined benefit pension and postretirement benefit plans, Net of Tax Amount	19,379	182	(21,938)
Other comprehensive loss, Pre-Tax Amount	(25,374)	43,523	(75,976)
Other comprehensive loss, Tax (Expense) Benefit	9,091	(15,585)	29,481
Other comprehensive (loss) income	$ (16,283)	$ 27,938	$ (46,495)