Accumulated Other Comprehensive Loss (Reclassifications out 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
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Long-term obligations	$ 179,528		$ 215,432		$ 384,410		$ 436,384
Securities gains (losses)	0		3		0		(42)
Amounts reclassified from accumulated other comprehensive income, net of tax	3,108	[1]	2,165	[1]	6,219	[1]	4,316	[1]
Unrealized Loss on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Long-term obligations	(819)	[1]	(776)	[1]	(1,632)	[1]	(1,525)	[1]
Income taxes	323	[1]	306	[1]	644	[1]	602	[1]
Amounts reclassified from accumulated other comprehensive income, net of tax	496	[1],[2]	470	[1],[2]	988	[1],[2]	923	[1],[2]
Unrealized Gains on Investment Securities Available for Sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains (losses)	0	[1]	3	[1]	0	[1]	3	[1]
Income taxes	0	[1]	(1)	[1]	0	[1]	(1)	[1]
Amounts reclassified from accumulated other comprehensive income, net of tax	0	[1],[2]	(2)	[1],[2]	0	[1],[2]	(2)	[1],[2]
Defined Benefit Pension Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Employee Benefits, prior service costs	(53)	[1]	(52)	[1]	(105)	[1]	(105)	[1]
Employee Benefits, actuarial gains	(4,241)	[1]	(2,738)	[1]	(8,493)	[1]	(5,475)	[1]
Total before taxes	(4,294)		(2,790)	[1]	(8,598)		(5,580)	[1]
Income taxes	1,682	[1]	1,093	[1]	3,367	[1]	2,185	[1]
Amounts reclassified from accumulated other comprehensive income, net of tax	$ 2,612	[1],[2]	$ 1,697	[1],[2]	$ 5,231	[1],[2]	$ 3,395	[1],[2]

[1] 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.

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