Retirement Plans (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Capitalization of pension and OPEB expense related to engineering and plant construction	$ 3,900,000	$ 4,900,000
Pension and other postretirement benefit expenses	3,053,000	5,018,000	97,100,000
Contributions to pension plan	19,600,000
Plan assets	1,229,500,000		1,216,500,000
Increase in plan assets	13,000,000
Percentage of increase in pension plan	1.00%
Positive investment returns	40,300,000
Cash contributions to pension plan	11,600,000
Benefit payments	38,900,000
Estimated contributions to pension plan in current fiscal year	100,000,000
Minimum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated Pension And OPEB Expense	65,000,000
Maximum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated Pension And OPEB Expense	$ 85,000,000