Self-Insurance Reserve for Losses and Loss Adjustment Expenses - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Self-Insurance Reserve for Losses and Loss Adjustment Expenses Disclosure [Abstract]
Increase (decrease) in provision for unpaid loss and loss adjustment expenses, current year		$ 15
Increase (decrease) in provision for unpaid loss and loss adjustment expenses, prior years	$ 11	$ 2

Amount of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 235
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-18)
-URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e575016-122915

Name:	us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration