Retirement Plans (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Contributory defined benefit pension plans	5
Contributions [Abstract]
Total contributions in fiscal year	$ 12,500,000		$ 12,500,000
Net periodic pension cost [Abstract]
Employer service cost - benefits earned during the period	956,000	986,000	2,857,000	2,970,000
Interest cost on projected benefit obligation	3,545,000	3,538,000	10,601,000	10,605,000
Expected return on plan assets	(4,930,000)	(4,321,000)	(14,741,000)	(12,941,000)
Net amortization of deferrals	528,000	524,000	1,579,000	1,569,000
Recognized actuarial loss	39,000	39,000	115,000	117,000
Net periodic pension cost	138,000	766,000	411,000	2,320,000
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Minimum expected return on plan assets (in hundredths)			4.70%
Maximum expected return on plan assets (in hundredths)			6.60%
Contributions [Abstract]
Contributions to defined benefit pension plans	4,200,000	3,500,000	10,300,000	8,100,000	13,100,000
Expected contributions in remainder of fiscal year	$ 2,200,000		$ 2,200,000