Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Components of net periodic benefit cost [Abstract]
Contribution made to pension and postretirement plans			$ 0
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	$ 15	$ 15	46	$ 45
Interest cost	343	337	1,029	997
Expected return on plan assets	(669)	(684)	(1,994)	(2,052)
Amortization of net loss (gain)	46	77	138	158
Amortization of prior service cost	0	0	0	0
Net periodic benefit	(265)	(255)	(781)	(852)
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	32	47	96	125
Interest cost	61	72	184	201
Expected return on plan assets	(180)	(182)	(540)	(543)
Amortization of net loss (gain)	(54)	(34)	(163)	(105)
Amortization of prior service cost	22	23	67	68
Net periodic benefit	$ (119)	$ (74)	$ (356)	$ (254)