Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Components of net periodic benefit cost
Contributions to qualified and non qualified pension plans	$ 1,924	$ 761
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	732	3,331
Interest cost	5,750	6,957
Expected return on plan assets	(6,449)	(8,803)
Amortization of prior service (benefit) cost	(39)	18
Recognized net actuarial loss	756	5,421
Curtailment loss	0	1,159
Net periodic pension benefit cost	750	8,083
Other Benefits [Member]
Components of net periodic benefit cost
Service cost	0	0
Interest cost	157	157
Expected return on plan assets	0	0
Amortization of prior service (benefit) cost	(57)	(122)
Recognized net actuarial loss	51	106
Curtailment loss	0	0
Net periodic pension benefit cost	$ 151	$ 141