Benefit Plans - Net Periodic Benefit Table (Details) (Pension Plans, USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension Plans
Net Periodic Benefit Credit [Abstract]
Interest cost	$ 2,200,000	$ 2,800,000
Expected return on plan assets	(3,175,000)	(3,612,000)
Amortization of net loss	620,000	259,000
Net periodic pension (credit)	(355,000)	(553,000)
Pension Plans Employer Contributions [Abstract]
Contributions by Employer	500,000	7,000,000
Estimated Total Employer Contributions for Current Fiscal Year	$ 4,700,000