Pension and Other Postretirement Benefits Net Periodic Benefit Cost (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
Pension Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 5,506	$ 5,534	$ 11,103	$ 12,059
Interest cost	6,610	5,982	13,409	11,957
Expected return on plan assets	(6,637)	(5,979)	(13,312)	(11,954)
Amortization of net actuarial loss	4,285	6,860	8,819	13,185
Amortization of prior service cost (gain)	230	338	476	688
Settlement loss			789	0
Net periodic benefit cost	9,994	12,735	21,284	25,935
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	602	647	1,227	1,322
Interest cost	843	711	1,668	1,436
Expected return on plan assets	0	0	0	0
Amortization of net actuarial loss	359	422	634	897
Amortization of prior service cost (gain)	(540)	(540)	(1,090)	(1,090)
Settlement loss			0	0
Net periodic benefit cost	$ 1,264	$ 1,240	$ 2,439	$ 2,565