Pension Benefit and Retirement Health and Life Insurance Benefits (Components of Net Periodic Benefit Cost) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 2,473	$ 4,596	$ 3,922
Interest cost		7,753	8,420	8,535
Expected return of plan assets		(11,247)	(9,892)	(10,559)
Amortization of prior service cost		124	463	597
Amortization of net loss		3,615	5,471	2,331
Settlement charge/(credit)		0	(2,073)	0
Special termination benefit		0	0	176
Curtailment charge	1,500	1,537	0	0
Net periodic benefit cost		4,255	11,131	5,002
Retirement Health and Life Insurance Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		627	630	693
Interest cost		262	364	413
Expected return of plan assets		0	0	0
Amortization of prior service cost		(230)	(451)	(627)
Amortization of net loss		204	313	421
Settlement charge/(credit)		0	0	0
Special termination benefit		0	1,592	0
Curtailment charge		0	0	0
Net periodic benefit cost		$ 863	$ 2,448	$ 900