Savings Plans, Pension Plans and Other Postretirement Employee Benefits (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
401(K) contributions by employer	$ 2,100,000	$ 2,100,000	$ 2,000,000
Decrease in accumulated postretirement benefit obligations				$ 76,700,000
Accumulated benefit obligation	379,500,000	375,500,000
Non-qualified pension plan and other postretirement employee benefit, estimated payments in next fiscal year	$ 5,800,000
Expected return on plan assets	6.50%
Health care cost trend rate assumed for next fiscal year	7.90%
Defined Benefit Plan, Assumption Health Care Cost Trend Rate for Next Fiscal Year	4.20%
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments in Level 3	$ 0	$ 0
Management Deferred Compensation Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Annual incentive plan, employee permitted minimum defer percentage	50.00%
Annual incentive plan, employee permitted maximum defer percentage	100.00%
Management Deferred Compensation Plan [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Basic salary defer percentage	50.00%
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated net loss to be amortized from Accumulated Other Comprehensive Loss into Net Periodic Benefit Cost	$ 15,400,000
Estimated prior service cost to be amortized from Accumulated Other Comprehensive Loss into Net Periodic Benefit Cost	$ 300,000
Expected return on plan assets	6.50%	6.75%	7.50%
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated net loss to be amortized from Accumulated Other Comprehensive Loss into Net Periodic Benefit Cost	$ 1,600,000
Estimated prior service cost to be amortized from Accumulated Other Comprehensive Loss into Net Periodic Benefit Cost	$ 8,900,000
Expected return on plan assets	0.00%	0.00%	0.00%