Credit Agreement and Senior Notes - Summary of Carrying Value of Senior Notes (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Total maturities of senior notes, net of unamortized discount	$ 2,494,143	$ 1,496,066
Less: Current portion of long-term debt	249,954
Total Long-term debt	2,244,189	1,496,066
5.15% Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Senior Notes	249,954	249,882
4.875% Senior Notes due 2015 [Member]
Debt Instrument [Line Items]
Senior Notes	249,898	249,837
5.875% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Senior Notes	499,551	499,480
3.45% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Senior Notes	248,988
5.70% Senior Notes due 2039 [Member]
Debt Instrument [Line Items]
Senior Notes	496,919	496,867
4.875% Senior Notes due 2043 [Member]
Debt Instrument [Line Items]
Senior Notes	$ 748,833

Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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