Retirement Plans, Estimated Amounts That Will be Amortized from Accumulated Other Comprehensive Income Into Net Periodic Benefit Cost (Details) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	$ 5,477
Prior service cost (credit)	0
Estimated amounts to be amortized	5,477
SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	28
Prior service cost (credit)	0
Estimated amounts to be amortized	28
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	(668)
Prior service cost (credit)	0
Estimated amounts to be amortized	$ (668)

Amount included in accumulated other comprehensive income (AOCI) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position, including gain (loss), prior service cost (credit), and transition asset (obligation).

No definition available.

Name:	us-gaap_DefinedBenefitPlanAmountToBeAmortizedFromAccumulatedOtherComprehensiveIncomeLossNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration