Accumulated Other Comprehensive Loss (Components of AOCI) (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) [Line Items]
Beginning balance	$ (79,905)		$ (66,416)		$ (82,106)	[1]	$ (66,574)
Other comprehensive income (loss) before reclassifications	(23,379)		1,844		(24,289)		(149)
Amounts reclassified from accumulated other comprehensive income	3,108	[2]	2,165	[2]	6,219	[2]	4,316	[2]
Net current period other comprehensive income (loss)	(20,271)		4,009		(18,070)		4,167
Ending balance	(100,176)	[3]	(62,407)	[3]	(100,176)	[3]	(62,407)	[3]
Unrealized Loss on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(5,799)	[4]	(6,248)	[4]	(6,292)	[4]	(6,483)	[4]
Other comprehensive income (loss) before reclassifications	344	[4]	(891)	[4]	345	[4]	(1,109)	[4]
Amounts reclassified from accumulated other comprehensive income	496	[2],[4]	470	[2],[4]	988	[2],[4]	923	[2],[4]
Net current period other comprehensive income (loss)	840	[4]	(421)	[4]	1,333	[4]	(186)	[4]
Ending balance	(4,959)	[4]	(6,669)	[4]	(4,959)	[4]	(6,669)	[4]
Unrealized Gains on Investment Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	19,606	[4]	14,340	[4]	20,517	[4]	16,115	[4]
Other comprehensive income (loss) before reclassifications	(23,723)	[4]	2,735	[4]	(24,634)	[4]	960	[4]
Amounts reclassified from accumulated other comprehensive income	0	[2],[4]	(2)	[2],[4]	0	[2],[4]	(2)	[2],[4]
Net current period other comprehensive income (loss)	(23,723)	[4]	2,733	[4]	(24,634)	[4]	958	[4]
Ending balance	(4,117)	[4]	17,073	[4]	(4,117)	[4]	17,073	[4]
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(93,712)	[4]	(74,508)	[4]	(96,331)	[4]	(76,206)	[4]
Other comprehensive income (loss) before reclassifications	0	[4]	0	[4]	0	[4]	0	[4]
Amounts reclassified from accumulated other comprehensive income	2,612	[2],[4]	1,697	[2],[4]	5,231	[2],[4]	3,395	[2],[4]
Net current period other comprehensive income (loss)	2,612	[4]	1,697	[4]	5,231	[4]	3,395	[4]
Ending balance	$ (91,100)	[4]	$ (72,811)	[4]	$ (91,100)	[4]	$ (72,811)	[4]

[1] Derived from 2012 Annual Report on Form 10-K.

[2] Amounts in parentheses indicate debits to profit/loss.Details about accumulated other comprehensive loss Amount reclassified from accumulated other comprehensive loss1 Affected line item in the statement where net income is presented (dollars in thousands) Six months ended June 30, 2013 Gains and losses on cash flow hedges Interest rate swap contracts $(1,632) Long-term obligations 644 Income taxes $(988) Net of taxUnrealized gains and losses on available for sale securities $— Securities gains (losses) — Income taxes $— Net of taxAmortization of defined benefit pension items Prior service costs $(105) Employee benefits Actuarial gains (8,493) Employee benefits (8,598) Total before taxes 3,367 Income taxes $(5,231) Net of taxTotal reclassifications for the period $(6,219) Six months ended June 30, 2012 Gains and losses on cash flow hedges Interest rate swap contracts $(1,525) Long-term obligations 602 Income taxes $(923) Net of tax Unrealized gains and losses on available for sale securities $3 Securities gains (losses) (1) Income taxes $2 Net of tax Amortization of defined benefit pension items Prior service costs $(105) Employee benefits Actuarial gains (5,475) Employee benefits (5,580) Total before taxes 2,185 Income taxes $(3,395) Net of taxTotal reclassifications for the period $(4,316) 1 Amounts in parentheses indicate debits to profit/loss.

[3] Unaudited

[4] All amounts are net of tax. Amounts in parentheses indicate debits.