Pension and Other Post-Retirement Benefits Components of Net Periodic Pension Expense (Details) - Pension Plans - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 4,760	$ 5,248	$ 9,520	$ 10,496
Expected return on plan assets	(5,518)	(6,050)	(11,035)	(12,100)
Amortization of actuarial loss	2,830	1,907	5,660	3,814
Total	$ 2,072	$ 1,105	$ 4,145	$ 2,210