Long-Term Debt Interest Rates (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 08, 2014	Nov. 24, 2014	Dec. 31, 2013	Dec. 10, 2010	Jan. 20, 2005
1.875% Senior Notes
Debt Instrument [Line Items]
Unamortized discount	$ 6,605
Debt instrument, interest rate	1.875%	1.875%
3.00% Senior Notes
Debt Instrument [Line Items]
Unamortized discount	306
Debt instrument, interest rate	3.00%		3.00%
4.15% Senior Notes
Debt Instrument [Line Items]
Unamortized discount	1,439
Debt instrument, interest rate	4.15%		4.15%
4.50% Senior Notes
Debt Instrument [Line Items]
Unamortized discount	1,871			2,186
Debt instrument, interest rate	4.50%			4.50%	4.50%
5.10% Senior Notes
Debt Instrument [Line Items]
Unamortized discount	3			36
Debt instrument, interest rate	5.10%			5.10%		5.10%
5.45% Senior Notes
Debt Instrument [Line Items]
Unamortized discount	$ 1,029
Debt instrument, interest rate	5.45%		5.45%