Pension Plans and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Benefits
Benefit Plans
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	2,485	2,455	5,021	4,965
Expected return on plan assets	(3,058)	(3,634)	(6,116)	(7,267)
Recognized net actuarial loss (gain)	673	729	1,407	1,486
Amortization of prior service cost	48	48	95	95
Net periodic cost (benefit)	148	(402)	407	(721)
Other Postretirement Benefits
Benefit Plans
Service cost	460	596	932	1,065
Interest cost	234	226	497	502
Expected return on plan assets	0	0	0	0
Recognized net actuarial loss (gain)	(145)	0	(212)	0
Amortization of prior service cost	0	0	0	0
Net periodic cost (benefit)	$ 549	$ 822	$ 1,217	$ 1,567