Pension Plans and Other Postretirement Benefits (Details-5) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 355,110	$ 330,886
Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	284	300
Equity Securities [Member] | U.S. Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	107,406	98,949
Equity Securities [Member] | U.S. Mid Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25,966	22,446
Equity Securities [Member] | U.S. Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	33,836	27,561
Equity Securities [Member] | International Blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	59,054	55,948
Fixed Income Securities [Member] | Short-Term Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,318	3,388
Fixed Income Securities [Member] | High Yield Bond [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17,978	16,225
Fixed Income Securities [Member] | Long Duration Bond [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	71,512	73,112
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	29,441	27,231
Insurance Continuance Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,514	1,518
Fixed Rate Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 3,801	$ 4,208