Retirement Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Retirement Income Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1,964	$ 1,627	$ 5,891	$ 4,880
Interest cost	3,501	3,253	10,504	9,760
Expected return on plan assets	(3,991)	(3,919)	(11,972)	(11,756)
Amortization of unrecognized net actuarial loss	1,696	367	5,086	1,102
Total net periodic cost	3,170	1,328	9,509	3,986
Retirement Life Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0	0	0	0
Interest cost	64	73	190	219
Expected return on plan assets	0	0	0	0
Amortization of unrecognized net actuarial loss	13	14	41	40
Total net periodic cost	$ 77	$ 87	$ 231	$ 259