Defined Benefit Postretirement Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Defined Benefit Plan Disclosure [Line Items]
Transition obligation period of recognition			20 years
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	$ 587	$ 604	$ 1,174	$ 1,209
Interest cost	1,040	830	2,080	1,659
Expected return on plan assets	(2,175)	(1,929)	(4,350)	(3,858)
Net amortization	25	711	50	1,314
Total cost (benefit)	(523)	216	(1,046)	324
Other Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	4	6	8	12
Interest cost	90	75	180	150
Expected return on plan assets	0	0	0	0
Net amortization	(6)	(1)	(12)	222
Total cost (benefit)	$ 88	$ 80	$ 176	$ 384