Pension Benefit and Other Postretirement Benefit Plans (Components of Net Periodic Benefit Cost) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 1,254
Interest cost	2,018	2,061
Expected return on plan assets	(3,227)	(2,716)
Amortization of prior service cost		93
Amortization of net loss	183	1,476
Settlement charge	110
Net periodic benefit cost (income)	(916)	2,168
Retirement Health and Life Insurance Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	160	170
Interest cost	83	71
Expected return on plan assets
Amortization of prior service cost		(58)
Amortization of net loss	31	83
Settlement charge
Net periodic benefit cost (income)	$ 274	$ 266