Accumulated Other Comprehensive Loss (Components of AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (100,176)		$ (62,407)		$ (82,106)	[1]	$ (66,574)
Other comprehensive income (loss) before reclassifications	1,963		8,279		(22,326)		8,130
Amounts reclassified from accumulated other comprehensive income	2,668	[2]	2,142	[2]	8,887	[2]	6,458	[2]
Net current period other comprehensive income (loss)	4,631		10,421		(13,439)		14,588
Ending balance	(95,545)	[3]	(51,986)		(95,545)	[3]	(51,986)
Unrealized Loss on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(4,959)	[4]	(6,670)	[4]	(6,292)	[4]	(6,484)	[4]
Other comprehensive income (loss) before reclassifications	(330)	[4]	(555)	[4]	15	[4]	(1,664)	[4]
Amounts reclassified from accumulated other comprehensive income	431	[2],[4]	465	[2],[4]	1,419	[2],[4]	1,388	[2],[4]
Net current period other comprehensive income (loss)	101	[4]	(90)	[4]	1,434	[4]	(276)	[4]
Ending balance	(4,858)	[4]	(6,760)	[4]	(4,858)	[4]	(6,760)	[4]
Unrealized Gains on Investment Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(4,117)	[4]	17,073	[4]	20,517	[4]	16,115	[4]
Other comprehensive income (loss) before reclassifications	2,293	[4]	8,834	[4]	(22,341)	[4]	9,794	[4]
Amounts reclassified from accumulated other comprehensive income	0	[2],[4]	(19)	[2],[4]	0	[2],[4]	(21)	[2],[4]
Net current period other comprehensive income (loss)	2,293	[4]	8,815	[4]	(22,341)	[4]	9,773	[4]
Ending balance	(1,824)	[4]	25,888	[4]	(1,824)	[4]	25,888	[4]
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(91,100)	[4]	(72,810)	[4]	(96,331)	[4]	(76,205)	[4]
Other comprehensive income (loss) before reclassifications	0	[4]	0	[4]	0	[4]	0	[4]
Amounts reclassified from accumulated other comprehensive income	2,237	[2],[4]	1,696	[2],[4]	7,468	[2],[4]	5,091	[2],[4]
Net current period other comprehensive income (loss)	2,237	[4]	1,696	[4]	7,468	[4]	5,091	[4]
Ending balance	$ (88,863)	[4]	$ (71,114)	[4]	$ (88,863)	[4]	$ (71,114)	[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) Nine months ended September 30, 2013 Gains and losses on cash flow hedges Interest rate swap contracts $(2,463) Long-term obligations 1,044 Income taxes $(1,419) Net incomeUnrealized gains and losses on available for sale securities $— Securities gains (losses) — Income taxes $— Net incomeAmortization of defined benefit pension items Prior service costs $(158) Employee benefits Actuarial gains (12,738) Employee benefits (12,896) Income before income taxes 5,428 Income taxes $(7,468) Net incomeTotal reclassifications for the period $(8,887) Nine months ended September 30, 2012 Gains and losses on cash flow hedges Interest rate swap contracts $(2,294) Long-term obligations 906 Income taxes $(1,388) Net income Unrealized gains and losses on available for sale securities $34 Securities gains (losses) (13) Income taxes $21 Net income Amortization of defined benefit pension items Prior service costs $(158) Employee benefits Actuarial gains (8,210) Employee benefits (8,368) Income before income taxes 3,277 Income taxes $(5,091) Net incomeTotal reclassifications for the period $(6,458) 1 Amounts in parentheses indicate debits to profit/loss.

[3] Unaudited

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