Credit Agreement and Long-Term Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended													12 Months Ended				12 Months Ended							12 Months Ended
	Dec. 31, 2012 Y	Dec. 31, 2012 Federal Funds Rate [Member]	Dec. 31, 2012 One Month Euro Dollar Rate [Member]	Dec. 31, 2012 ABR Loans [Member]	Dec. 31, 2012 Eurodollar Loans [Member]	Dec. 31, 2012 5.70% Senior Notes [Member]	Dec. 31, 2011 5.70% Senior Notes [Member]	Dec. 31, 2012 5.875% Senior Notes [Member]	Dec. 31, 2011 5.875% Senior Notes [Member]	Dec. 31, 2012 4.875% Senior Notes [Member]	Dec. 31, 2011 4.875% Senior Notes [Member]	Dec. 31, 2012 5.15% Senior Notes [Member]	Dec. 31, 2011 5.15% Senior Notes [Member]	Dec. 31, 2012 Minimum [Member]	Dec. 31, 2012 Minimum [Member] Performance Letters of Credit [Member]	Dec. 31, 2012 Minimum [Member] ABR Loans [Member]	Dec. 31, 2012 Minimum [Member] Eurodollar Loans [Member]	Dec. 31, 2012 Maximum [Member]	Dec. 31, 2012 Maximum [Member] Performance Letters of Credit [Member]	Dec. 31, 2012 Maximum [Member] ABR Loans [Member]	Dec. 31, 2012 Maximum [Member] Eurodollar Loans [Member]	Dec. 31, 2012 Letters of Credit [Member]	Dec. 31, 2012 Letters of Credit [Member] Minimum [Member]	Dec. 31, 2012 Letters of Credit [Member] Maximum [Member]	Dec. 31, 2012 Swing Line Loan Facility [Member]	Dec. 31, 2012 Senior Unsecured Credit Facilities [Member]
Debt Instrument [Line Items]
Term of Credit agreement	5
Initiation period of Credit agreement	Sep. 28, 2012
Amount available for general purposes	$ 750																					$ 250			$ 75
Maturity period of Credit agreement																										Sep. 28, 2017
Basis point increase		0.0050	0.0100
Interest margin				0.00%	1.00%											0.00%	0.75%			0.25%	1.25%
Swingline loans bear interest description																									Swingline loans bear interest, at our option, at a rate per annum equal to (i) the ABR plus the applicable interest margin for ABR loans or (ii) the daily one-month Eurodollar Rate plus the applicable interest margin for Eurodollar loans
Commitment fee on unused commitments														0.06%				0.20%
Participation fees for letters of credit															0.375%				0.625%				0.75%	1.25%
Ratio of consolidated indebtedness to total capitalization	0.60
Amount outstanding under credit agreement	$ 0
Interest rate of senior notes						5.70%	5.70%	5.875%	5.875%	4.875%	4.875%	5.15%	5.15%
Notice period for redemption of notes	15-60 days