Short-Term Financing - Additional Information (Detail) (USD $)	0 Months Ended					12 Months Ended						12 Months Ended
	Dec. 29, 2010	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Commercial paper (secured) program	Dec. 31, 2012 Commercial paper (secured)	Dec. 31, 2013 Commercial paper (secured) Minimum	Dec. 31, 2013 Commercial paper (secured) Maximum	Dec. 31, 2013 Commercial paper (secured) CP Series A	Dec. 31, 2013 Commercial paper (secured) CP Series II A	Dec. 31, 2013 Commercial paper (secured) CP Series III A	Dec. 31, 2013 Line of Credit [Member] Uncommitted Credit Facility [Member] banks	Dec. 31, 2013 Line of Credit [Member] Committed Credit Facility [Member]	Dec. 31, 2013 Committed Credit Facility [Member]	Dec. 31, 2013 Committed Credit Facility [Member] Covenant Requirement
Short-term Debt [Line Items]
Senior secured commercial paper notes, maturity period						27 days	270 days
Number of commercial paper programs				3
Weighted average maturity period								132 days	107 days	31 days
Debt term	3 years											1 year
Line of credity, maximum borrowing capacity											$ 185,000,000	$ 250,000,000	$ 250,000,000
Minimum net capital required														120,000,000
Short-term financing		$ 514,711,000	$ 477,014,000	$ 280,294,000	$ 304,439,000						$ 0	$ 0
Number of banks											2