Pension Plan and Postretirement Benefits Other Than Pension (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Benefits
Components of net periodic benefit cost:
Service cost	$ 11,011,000	$ 9,373,000	$ 7,101,000
Interest cost	7,711,000	7,570,000	7,195,000
Expected return on plan assets	(11,185,000)	(8,799,000)	(8,764,000)
Actuarial loss amortization	4,567,000	4,563,000	1,805,000
Prior service cost amortization	555,000	555,000	555,000
Transition obligation amortization	5,000	5,000	5,000
Net periodic benefit cost	12,664,000	13,267,000	7,897,000
Amounts that will be amortized from accumulated other comprehensive income into net periodic benefit cost in next fiscal year
Estimated net gain (loss) that will be amortized from accumulated other comprehensive income into net periodic benefit cost	(1,200,000)
Estimated prior service cost that will be amortized from accumulated other comprehensive income into net periodic benefit cost	520,000
Estimated transition obligation that will be amortized from accumulated other comprehensive income into net periodic benefit cost	5,000
Weighted average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	4.22%	4.99%	6.00%
Expected return on plan assets (as a percent)	7.75%	7.75%	7.75%
Rate of compensation increase (as a percent)	3.99%	4.04%	3.86%
Expected benefit payments
2014	8,135,000
2015	7,973,000
2016	10,431,000
2017	11,414,000
2018	11,336,000
2019 through 2023	71,145,000
Total	120,434,000
Expected contribution in the next fiscal year	10,000,000
Pension Benefits | Segment Discontinued Operations
Components of net periodic benefit cost:
Net periodic benefit cost		749,000	543,000
Pension Benefits | Maximum
Expected benefit payments
Expected contribution in the next fiscal year	20,000,000
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	788,000	693,000	558,000
Interest cost	361,000	400,000	402,000
Actuarial loss amortization		12,000
Prior service cost amortization	55,000	55,000	55,000
Net periodic benefit cost	1,204,000	1,160,000	1,015,000
Amounts that will be amortized from accumulated other comprehensive income into net periodic benefit cost in next fiscal year
Estimated net gain (loss) that will be amortized from accumulated other comprehensive income into net periodic benefit cost	17,000
Estimated prior service cost that will be amortized from accumulated other comprehensive income into net periodic benefit cost	55,000
Weighted average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	4.18%	5.00%	6.00%
Expected benefit payments
2014	260,000
2015	291,000
2016	356,000
2017	393,000
2018	489,000
2019 through 2023	3,458,000
Total	5,247,000
Contributions by participants	321,000	337,000	359,000
Other Postretirement Benefits | Segment Discontinued Operations
Components of net periodic benefit cost:
Net periodic benefit cost		$ 749,000	$ 543,000