Accounting Policies (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Oct. 01, 2010
Health Insurance Costs [Abstract]
Number of days in advance of the beginning of a reporting quarter United establishes cash funding rates	90 days
Required accumulated cash surplus	$ 9,000		$ 9,000
Required deposit equal to approximately one day of claims funding activity	3,500
Amount which plan costs were less than the net premiums paid and owed	17,800
Prepaid health insurance, current	8,800
Premiums owed to United	8,900
Benefits costs reduction related to run-off	800
Benefits costs incurred related to run-off		$ 2,400
Workers' Compensation Costs [Abstract]
Company's maximum economic burden for the first layer of claims per occurrence				$ 1,000
Decrease Increase in accrued workers' compensation costs for changes in estimated losses	$ 500	$ 3,000
Company's maximum aggregate economic burden for claims in excess of 1 million per policy year				$ 5,000
U.S. Treasury rates that correspond with the weighted average estimated claim payout period (in hundredths)	1.00%	1.00%
Incurred but not paid workers compensation liabilities [Abstract]
Beginning balance, January 1,	$ 136,088	$ 120,833
Accrued claims	49,607	39,130
Present value discount	(1,816)	(1,418)
Paid claims	(28,735)	(28,314)
Ending balance	155,144	130,231
Current portion of accrued claims	43,056	57,222
Long-term portion of accrued claims	112,088	73,009	92,048
Workers compensation administrative fees accrued	2,700
Undiscounted accrued workers' compensation costs	$ 164,700	140,000
Time period incurred claims expected to be paid recorded as restricted cash	1 year
Time period incurred claims expected to be paid, included in deposits, a long-term asset	Greater than 1 year
Return of Excess Claim Funds Net of Additional Amounts Paid in Claim Funds for Prior Policy Years	$ 5,300
Additional claim funds paid related to ACE Program		$ 7,200
Restricted cash - worker's compensation	43,056		44,040
Deposits workers compensation	$ 121,172		$ 113,934
Time period estimate of incurred claim costs to be paid included in short-term liabilities	1 year
Time period incurred claims expected to be paid, included in long-term liabilities	Greater than 1 year