Financial Instruments and Derivatives - Carrying Amount and Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Debt Disclosure [Abstract]
Long-term debt, net of current portion, Carrying Amount	$ 947,568	$ 1,099,454	[1]
Long-term debt, net of current portion, Fair Value	$ 1,067,086	$ 1,214,292

[1] The year-end condensed consolidated balance sheet data was derived from audited financial statements but does not include all disclosures required by generally accepted accounting principles.