Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Taxes [Abstract]

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

(dollars in thousands)		2016		2015		2014
Current:
Federal	$	25,908	$	29,888	$	24,809
State		5,888		3,325		1,237
Deferred:
Federal		6,020		(188)		2,559
State		(317)		(24)		676
	$	37,499	$	33,001	$	29,281

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

(dollars in thousands)		2016		2015		2014
Income taxes at federal statutory rate	$	43,631	$	32,316	$	29,282
State income taxes, net of federal income tax benefit		2,413		1,112		1,436
Deferred tax on gain on bargain purchase		(8,358)		-		-
Other		(187)		(427)		(1,437)
Provision for income taxes (effective tax rate 30.1%,  35.7% and 35.0%, respectively)	$	37,499	$	33,001	$	29,281

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

(dollars in thousands)		2016		2015
Deferred tax assets:
Accounts receivable	$	586	$	813
Compensated absences		1,076		983
Employment incentives		9,826		3,143
Employee benefit plans		9,243		10,485
General liability insurance		4,359		4,048
Postretirement benefit obligations		6,484		5,906
Net operating loss carryforwards		5,600		5,926
Other		2,224		2,173
Total deferred tax assets		39,398		33,477
Deferred tax liabilities:
Inventories		(7,619)		(6,808)
Unrealized gains on marketable securities		(3,382)		(3,323)
Nondeductible accruals and other		(7,517)		(9,240)
Depreciation		(140,325)		(111,126)
Total deferred tax liabilities		(158,843)		(130,497)
Net deferred tax liability	$	(119,445)	$	(97,020)

Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]

(dollars in thousands)		2016		2015
Unrecognized tax benefits at beginning of year	$	1,264	$	-
Increases based on tax positions related to the current year		1,563		1,264
Additions for tax positions of prior year		297		-
Reductions for tax positions of prior years		-		-
Settlements		-		-
Expiration of the statute of limitations for assessment of taxes		-		-
Unrecognized tax benefits at end of year	$	3,124	$	1,264