Pensions (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
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			$ 1,593
Estimated employer contributions	1,593		1,593
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	297	263	891	788
Interest cost	320	322	960	966
Expected return on plan assets	(411)	(361)	(1,233)	(1,082)
Amortization of actuarial loss	174	161	523	481
Amortization of prior service cost	3	4	8	13
Rate-regulated adjustment	15	9	45	28
Net periodic pension expense	$ 398	$ 398	$ 1,194	$ 1,194