Retirement Plans and Other Postretirement Benefits - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan qualified retirement plan employer contributions current fiscal year	$ 2,000	$ 2,000
Employee hire date no longer eligible for noncontributory retirement plan		Dec. 08, 2009
Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, non-qualified plans, estimated employer contributions for next fiscal year			$ 166
Defined benefit plan, contributions by employer		$ 98
Defined benefit plan, benefits paid		1,200
Other Post Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected employer contributions for next fiscal year			$ 113
Defined benefit plan, contributions by employer		47
Defined benefit plan, benefits paid		$ 0