Defined Benefit Postretirement Plans (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]
Transition obligation amortization period			20 years
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	$ 604	$ 757	$ 1,813	$ 2,270
Interest cost	830	774	2,489	2,322
Expected return on plan assets	(1,929)	(1,676)	(5,786)	(5,026)
Net amortization	711	992	2,025	2,710
Total cost (benefit)	216	847	541	2,276
Other Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	6	6	18	16
Interest cost	75	40	224	119
Expected return on plan assets	0	0	0	0
Net amortization	(2)	(3)	219	(8)
Total cost (benefit)	$ 79	$ 43	$ 461	$ 127