Credit Agreement and Long-Term Debt - Summary of Long-Term Debt (Parenthetical) (Detail)	Dec. 31, 2012	Dec. 31, 2011
5.15% Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	5.15%	5.15%
4.875% Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	4.875%	4.875%
5.875% Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	5.875%	5.875%
5.70% Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate of senior notes	5.70%	5.70%