Employee Benefit Plans (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension
Fair value of plan assets	$ 156,678	$ 206,309
Actuarial assumptions:
Expected rate of return on plan assets for 2016 net periodic benefit cost (as a percent)	7.00%
Equity securities
Pension
Target allocations for plan assets (as a percent)	65.00%
Common Stock
Pension
Fair value of plan assets	$ 8,954	18,752
Equity funds - large cap index
Pension
Fair value of plan assets	$ 85,874	108,189
Fixed income securities
Pension
Target allocations for plan assets (as a percent)	35.00%
Fixed income funds - diversified bond
Pension
Fair value of plan assets	$ 61,300	78,503
Short term investment funds
Pension
Fair value of plan assets	550	865
Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension
Fair value of plan assets	8,954	18,752
Quoted Prices in Active Markets for Identical Assets (Level 1) | Common Stock
Pension
Fair value of plan assets	8,954	18,752
Significant other observable inputs (Level 2)
Pension
Fair value of plan assets	147,724	187,557
Significant other observable inputs (Level 2) | Equity funds - large cap index
Pension
Fair value of plan assets	85,874	108,189
Significant other observable inputs (Level 2) | Fixed income funds - diversified bond
Pension
Fair value of plan assets	61,300	78,503
Significant other observable inputs (Level 2) | Short term investment funds
Pension
Fair value of plan assets	550	865
Pension
Pension
Fair value of plan assets	156,678	$ 206,309	$ 188,386
Expected company contribution	9,300
Projected benefit payments
2016	17,430
2017	14,938
2018	15,602
2019	12,572
2020	13,067
2021 through 2025	62,046
Projected benefit payments	135,655
Other Postretirement Benefits
Pension
Expected company contribution	2,900
Projected benefit payments
2016	2,992
2017	3,232
2018	3,555
2019	3,633
2020	3,725
2021 through 2025	18,393
Projected benefit payments	35,530
Annual effects of one-percentage point change in the assumed health care cost trend rates
1-Percentage Point Increase, Effect on total of service and interest costs components	263
1-Percentage Point Decrease, Effect on total of service and interest costs components	(207)
1-Percentage Point Increase, Effect on postretirement benefit obligation	3,925
1-Percentage Point Decrease, Effect on postretirement benefit obligation	$ (3,154)