Pension and Other Post Retirement Benefits (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2012 Postretirement_Plan	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Number of Postretirement Plans	2
Pension and Other Post Retirement Details (Textual) [Abstract]
Collective bargaining agreement, beginning	2012-01
Previous collective bargaining agreement, expiration	2011-08
Defined benefit plan, employer contributions	$ 1,600,000	$ 1,400,000	$ 0
Multiemployer plan contributions	5.00%
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of days notice upon which redemptions from real estate funds are available	45 days
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of days notice upon which redemptions from real estate funds are available	60 days
Defined Benefit Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Aggregate accumulated benefit obligation	453,700,000	408,900,000
Unrecognized net actuarial loss (gain)	9,900,000	7,200,000	6,000,000
Prior Service Credit	(1,000,000)	(1,000,000)	(1,000,000)
Defined benefit plan, estimated future employer contributions in next fiscal year	7,000,000
Pension and Other Post Retirement Details (Textual) [Abstract]
Defined benefit plan, employer contributions	2,100,000	2,200,000
Other Post-retirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized net actuarial loss (gain)	(100,000)	(300,000)	(300,000)
Prior Service Credit	(100,000)	(100,000)	(100,000)
Pension and Other Post Retirement Details (Textual) [Abstract]
Defined benefit plan, employer contributions	$ 3,800,000	$ 4,200,000