Retirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,460	$ 2,794	$ 7,381	$ 8,251
Interest cost	2,542	2,144	7,625	6,292
Expected return on plan assets	(2,822)	(2,124)	(8,468)	(6,367)
Amortization of prior service cost	13	12	38	37
Amortization of net (income) loss	1,173	2,064	3,356	5,872
FAS 88 settlement charge	5,269		5,269
Net periodic benefit cost	8,635	4,890	15,201	14,085
Pension contributions	0	0	0	0
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	407	462	1,221	1,460
Interest cost	342	291	1,026	845
Amortization of net (income) loss	82	185	246	493
Net periodic benefit cost	$ 831	$ 938	$ 2,493	$ 2,798