Employee Benefit Plans (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Pension Plan
Benefit Plan Disclosure
Excess of benefit obligation over plan assets, net amount recognized	$ 13,004
Amounts recognized in the balance sheet consist of:
Accrued benefit liability—current	128
Accrued benefit liability—noncurrent	12,876
Net amount recognized	13,004
Summary of plan
Projected benefit obligation	44,400
Accumulated benefit obligation	44,400
Fair value of plan assets	31,395
Assumptions used
Discount rate (as a percent)	3.18%
Postretirement Benefit Plan
Benefit Plan Disclosure
Excess of benefit obligation over plan assets, net amount recognized	18,052
Amounts recognized in the balance sheet consist of:
Accrued benefit liability—current	628
Accrued benefit liability—noncurrent	17,424
Net amount recognized	18,052
Summary of plan
Projected benefit obligation	18,052
Assumptions used
Discount rate (as a percent)	3.56%
Assumed health care cost trend rate (as a percent)	5.50%
1% Increase	3,221
1% Decrease	$ (2,519)