Defined Benefit Pension Plans Amounts reported in accumulated other comprehensive income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Amounts reported in accumulated other comprehensive income
Unrecognized net actuarial loss, Pretax	$ 17,636	$ 15,179
Unrecognized net actuarial loss, net of tax	10,577	9,158
Unrecognized prior service cost, pretax	82	96
Unrecognized prior service cost credit, net of tax	49	59
Amounts reported in accumulated other comprehensive income, pretax	17,718	15,275
Amounts reported in accumulated other comprehensive income (Loss), net of tax	10,626	9,217
Amortization of Costs Expected to be Recognized Next Year
Unrecognized net actuarial loss	1,387	860
Unrecognized prior service cost	14	9
Amortization of Costs Expected to be Recognized Next Year	1,401	869
For pension plans with accumulated benefit obligations in excess of plan assets
Projected benefit obligation	36,045	32,148	28,251
Accumulated benefit obligation	35,790	31,940
Fair value of plan assets	$ 22,957	$ 22,078	$ 23,867