Pensions (Details) (Pension Plans [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension Plans [Member]
Net Periodic Pension Cost [Abstract]
Service cost	$ 238	$ 297	$ 476	$ 594
Interest cost	361	320	722	640
Expected return on plan assets	(497)	(411)	(994)	(822)
Amortization of actuarial loss	32	175	63	349
Amortization of prior service cost	(3)	2	(6)	5
Rate-regulated adjustment	444	15	771	30
Net periodic pension expense	575	398	1,032	796
Employer Contributions [Abstract]
Estimated employer contributions			2,182
Contributions by employer			$ 2,182