Pension and Postretirement Benefits (Net Periodic Benefit Cost-Income) (Details) (USD $)	6 Months Ended	12 Months Ended	3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Pension [Member]		Jun. 30, 2010 Pension [Member]		Jun. 30, 2011 Pension [Member]		Jun. 30, 2010 Pension [Member]		Jun. 30, 2011 Postretirement [ Member]		Jun. 30, 2010 Postretirement [ Member]		Jun. 30, 2011 Postretirement [ Member]		Jun. 30, 2010 Postretirement [ Member]
Service cost			$ 1,500,000		$ 1,100,000		$ 2,900,000		$ 2,200,000		$ 100,000				$ 100,000
Interest cost			4,300,000		4,500,000		8,600,000		9,000,000		200,000		300,000		500,000		700,000
Expected return on assets			(6,100,000)	[1]	(5,600,000)	[1]	(12,200,000)	[1]	(11,200,000)	[1]		[1]	(100,000)	[1]	(100,000)	[1]	(200,000)	[1]
Actuarial (gain) / loss			2,200,000		1,800,000		4,500,000		3,600,000		(200,000)		(100,000)		(400,000)		(400,000)
Prior service cost			600,000		900,000		1,100,000		1,900,000								100,000
Net periodic benefit cost / (income) before adjustments			2,500,000		2,700,000		4,900,000		5,500,000		100,000		100,000		100,000		200,000
Difference between market related value of assets in years	5
Difference between actual and estimated asset returns in MRVA	3
Market related value of assets		$ 316,000,000

[1] For purposes of calculating the expected return on pension plan assets, under GAAP, the market-related value of assets (MRVA) is used. GAAP requires that the difference between actual plan asset returns and estimated plan asset returns be included in the MRVA equally over a period not to exceed five years. We use a methodology under which we include the difference between actual and estimated asset returns in the MRVA equally over a three year period. The MRVA used in the calculation of expected return on pension plan assets for the 2011 net periodic benefit cost was approximately $316 million.