Investments of Insurance Subsidiaries - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Amortized Cost And Fair Value Debt Securities [Abstract]
Investments subject to restrictions	$ 1	$ 9
Available for sale securities expected maturity of debt securities	3 years 9 months 18 days
Available for sale securities average scheduled maturity	5 years 4 months 24 days

Investments which are not defined as or included in marketable (debt, equity, or other) securities whose use is restricted in whole or in part, generally by contractual agreements or regulatory requirements. For use in an unclassified balance sheet.

No definition available.

Name:	us-gaap_RestrictedInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant