Workers' Compensation - Summarizes Aggregate Workers' Compensation Reserve Activity (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Workers Compensation Reserve [Abstract]
Workers' compensation claims liabilities, Beginning balance	$ 112,444	$ 70,564
Add: claims expense accrual:
Current period	16,351	12,677
Prior periods	3,801	3,452
Total expense accrual	20,152	16,129
Less: claim payments related to:
Current period	399	426
Prior periods	12,062	9,055
Total paid	12,461	9,481
Workers' compensation claims liabilities, Ending balance	120,135	77,212
Incurred but not reported (IBNR)	$ 69,185	$ 51,838

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

Name:	us-gaap_WorkersCompensationLiabilityCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant