Employee Benefit Plans (Details Textual) (USD $)	3 Months Ended		6 Months Ended				6 Months Ended	12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Qualified Pension [Member]	Dec. 31, 2012 Qualified Pension [Member]	Jun. 30, 2013 Post-retirement Healthcare [Member]	Dec. 31, 2013 Post-retirement Healthcare [Member]	Jun. 30, 2013 Minimum [Member] Qualified Pension [Member]
Employee Benefit Plans (Textual) [Abstract]
Expected employer contributions in current fiscal year					$ 11,200,000	$ 15,000,000			$ 7,400,000
Employer pension contribution year-to-date					3,800,000.0
Expected employer contribution amount, post-retirement healthcare plan								5,100,000
Employer contribution year-to-date							1,700,000
Expected benefit payments, remainder of fiscal year							$ 3,400,000
Actual return for qualified pension plan assets	(0.90%)	(1.90%)	2.90%	3.60%
Weighted average annualized expected return on qualified pension plan assets			7.60%