Defined Benefit Postretirement Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	$ 587	$ 604	$ 1,761	$ 1,813
Interest cost	1,040	830	3,120	2,489
Expected return on plan assets	(2,175)	(1,929)	(6,525)	(5,786)
Net amortization	25	711	75	2,025
Total cost (benefit)	(523)	216	(1,569)	541
Other Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	4	6	12	18
Interest cost	90	75	270	224
Expected return on plan assets	0	0	0	0
Net amortization	(6)	(2)	(18)	219
Total cost (benefit)	$ 88	$ 79	$ 264	$ 461