Pension Benefits and Other Postretirement Benefit Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Bear Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plan, required employer contribution			$ 400	$ 100
Defined benefit plan, contributions by employer				300
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 1,837	$ 1,872	5,519	5,658
Expected return on plan assets	(2,302)	(2,698)	(6,920)	(8,110)
Amortization of net loss (gain)	445	445	1,311	1,339
Net periodic (benefit) cost	(20)	(381)	(90)	(1,113)
Retirement Health and Life Insurance Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	12	37	68	111
Interest cost	20	19	51	57
Amortization of prior service cost (credit)	(411)	(373)	(1,191)	(1,119)
Amortization of net loss (gain)	16	(19)	(15)	(57)
Net periodic (benefit) cost	$ (363)	$ (336)	$ (1,087)	$ (1,008)