Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 Rate	Dec. 31, 2012 Rate	Dec. 31, 2011 Rate
Income before income taxes
Income before income taxes	$ 35,565	$ 40,658	$ 23,300
Provision for income taxes
Federal	7,089	15,853	3,065
State	2,183	2,239	2,277
Canadian	1,724	1,578	1,565
Total current	10,996	19,670	6,907
Deferred taxes	1,716	(3,607)	2,328
Total taxes on income	12,712	16,063	9,235
Tax rate reconciliation
Statutory U.S. federal tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefit	3.60%	3.90%	5.10%
Effect of Canadian income taxes	(1.60%)	(1.00%)	(1.20%)
Nondeductible expenses	1.90%	1.40%	2.50%
ESOP dividend deduction	(0.80%)	(0.70%)	(1.20%)
Audit settlements and uncertain tax adjustments	(2.20%)	1.80%	1.80%
Valuation allowance on foreign tax credits	0.00%	0.00%	(1.10%)
All other, net	(0.20%)	(0.90%)	(1.30%)
Effective income tax rate	35.70%	39.50%	39.60%
Current deferred tax assets and liabilities, net
Accrued compensation obligations	1,883	2,424
Self-insurance accruals	7,693	7,083
Prepaid expenses	(2,565)	(1,903)
Other, net	908	1,405
Deferred tax assets, current, gross	7,919	9,009
Less deferred tax asset valuation allowance	204	194
Net deferred income tax assets--current	7,715	8,815
Noncurrent deferred tax assets and liabilities, net
Self-insurance accruals	12,129	14,497
Intangibles	(234)	(341)
Accrued expenses and other liabilities	895	895
Accrued stock compensation	1,550	1,476
Defined benefit pension plans	1,873	4,698
Foreign tax credit carryforward	768	768
Other future deductible amounts, net	1,737	1,470
Deferred tax assets, gross, noncurrent	18,718	23,463
Less deferred tax asset valuation allowance	564	574
Deferred tax assets, net of valuation allowance	18,154	22,889
Property and equipment	20,718	21,830
Deferred tax liability, noncurrent	20,718	21,830
Net deferred tax assets--noncurrent	0	1,059
Net deferred tax liabilities--noncurrent	2,564	0
Undistributed Earnings of Foreign Subsidiaries	27,000
Unrecognized benefits and related interest and penalties
Unrecognized tax benefits	1,221	2,638	1,825
Portion, if recognized, would reduce tax expense and effective tax rate	942	1,933
Accrued interest on unrecognized tax benefits	41	142
Accrued penalties on unrecognized benefits	0	0
Reconciliation of unrecognized tax benefits
Balance, beginning of year	2,638	1,825	1,524
Additions based on tax positions related to the current year	370	667	279
Additions for tax positions of prior years	133	149	101
Reductions for tax positions of prior years	(1,155)	(3)	(61)
Reductions related to settlements with taxing authorities	(460)	0	0
Lapses in statutes of limitations	(305)	0	(18)
Balance, end of year	1,221	2,638	1,825
United States [Member]
Income before income taxes
Income before income taxes	29,203	35,414	18,261
Canada [Member]
Income before income taxes
Income before income taxes	$ 6,362	$ 5,244	$ 5,039