Pension Benefits and Other Postretirement Benefit Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2016
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 1,893,000	$ 1,839,000
Expected return on plan assets	(2,706,000)	(2,771,000)
Amortization of net loss (gain)	447,000	413,000
Net periodic benefit (income) cost	(366,000)	(519,000)
Retirement Health and Life Insurance Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	37,000	150,000
Interest cost	19,000	75,000
Amortization of prior service cost	(373,000)	0
Amortization of net loss (gain)	(19,000)
Net periodic benefit (income) cost	(336,000)	225,000
Non-Qualified Defined Benefit Pension Plan | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, contributions by employer	0	0
Bear Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plan, liabilities	$ 100,000	$ 0
Scenario, Forecast | Bear Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plan, liabilities			$ 300,000