Workers' Compensation Claims - Summarizes Aggregate Workers' Compensation Reserve Activity (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Workers Compensation Reserve [Abstract]
Workers' compensation claims liabilities, Beginning balance	$ 70,564	$ 51,193	$ 39,302
Claims expense accrual:
Current year	63,822	38,386	26,161
Prior years	23,445	12,344	9,978
Total expense accrual	87,267	50,730	36,139
Claims payments related to:
Current year	10,586	6,746	5,565
Prior years	34,801	24,613	18,683
Total paid	45,387	31,359	24,248
Workers' compensation claims liabilities, Ending balance	112,444	70,564	51,193
Incurred but not reported (IBNR)	$ 69,611	$ 47,992	$ 37,335

Carrying value as of the balance sheet date of obligations and payables pertaining to claims incurred of a workers compensation nature.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.15(5))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.15(a))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph a

-Article 7

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph 5

-Article 9

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