Credit Agreement and Senior Notes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Term of Credit agreement	5 years
Initiation period of Credit agreement	Sep. 28, 2012
Initial maturity date of Credit agreement	Sep. 28, 2017
Amount available for general purposes	$ 750,000,000
Ratio of consolidated indebtedness to total capitalization	0.60
Amount outstanding under credit agreement	0
Issuance of senior notes	1,000,000,000
Date of issuance of long term debt	Nov. 05, 2013
Proceeds from issuance	987,800,000
Semiannual Interest Payment Dates	May 1 and November 1
ABR Loans [Member]
Debt Instrument [Line Items]
Interest margin	0.00%
Eurodollar Loans [Member]
Debt Instrument [Line Items]
Interest margin	0.875%
Federal Funds Rate [Member]
Debt Instrument [Line Items]
Basis point increase	0.50%
One Month Eurodollar Rate [Member]
Debt Instrument [Line Items]
Basis point increase	1.00%
3.45% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Aggregate Principal Amount of senior notes	250,000,000
Maturity Date	Nov. 01, 2023
Semiannual Interest Payment Dates	May 1 and November 1
Accreted value of senior notes	248,988,000
4.875% Senior Notes due 2043 [Member]
Debt Instrument [Line Items]
Aggregate Principal Amount of senior notes	750,000,000
Maturity Date	Nov. 01, 2043
Semiannual Interest Payment Dates	May 1 and November 1
Accreted value of senior notes	748,833,000
5.15% Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Aggregate Principal Amount of senior notes	250,000,000
Maturity Date	Sep. 01, 2014
Semiannual Interest Payment Dates	March 1 and September 1
Accreted value of senior notes	249,954,000	249,882,000
4.875% Senior Notes due 2015 [Member]
Debt Instrument [Line Items]
Aggregate Principal Amount of senior notes	250,000,000
Maturity Date	Jul. 01, 2015
Semiannual Interest Payment Dates	January 1 and July 1
Accreted value of senior notes	249,898,000	249,837,000
5.875% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Aggregate Principal Amount of senior notes	500,000,000
Maturity Date	May 01, 2019
Semiannual Interest Payment Dates	May 1 and November 1
Accreted value of senior notes	499,551,000	499,480,000
5.70% Senior Notes due 2039 [Member]
Debt Instrument [Line Items]
Aggregate Principal Amount of senior notes	500,000,000
Maturity Date	Oct. 15, 2039
Semiannual Interest Payment Dates	April 15 and October 15
Accreted value of senior notes	496,919,000	496,867,000
Minimum [Member]
Debt Instrument [Line Items]
Commitment fee on unused commitments	0.06%
Minimum [Member] | ABR Loans [Member]
Debt Instrument [Line Items]
Interest margin	0.00%
Minimum [Member] | Eurodollar Loans [Member]
Debt Instrument [Line Items]
Interest margin	0.75%
Minimum [Member] | 3.45% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	15 days
Minimum [Member] | 4.875% Senior Notes due 2043 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	15 days
Minimum [Member] | 5.15% Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	15 days
Minimum [Member] | 4.875% Senior Notes due 2015 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	15 days
Minimum [Member] | 5.875% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	15 days
Minimum [Member] | 5.70% Senior Notes due 2039 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	15 days
Maximum [Member]
Debt Instrument [Line Items]
Commitment fee on unused commitments	0.20%
Maximum [Member] | ABR Loans [Member]
Debt Instrument [Line Items]
Interest margin	0.25%
Maximum [Member] | Eurodollar Loans [Member]
Debt Instrument [Line Items]
Interest margin	1.25%
Maximum [Member] | 3.45% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	60 days
Maximum [Member] | 4.875% Senior Notes due 2043 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	60 days
Maximum [Member] | 5.15% Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	60 days
Maximum [Member] | 4.875% Senior Notes due 2015 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	60 days
Maximum [Member] | 5.875% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	60 days
Maximum [Member] | 5.70% Senior Notes due 2039 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	60 days
Swingline Loan Facility [Member]
Debt Instrument [Line Items]
Amount available for general purposes	75,000,000
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.
Performance Letters of Credit [Member] | Minimum [Member]
Debt Instrument [Line Items]
Participation fees for letters of credit	0.375%
Performance Letters of Credit [Member] | Maximum [Member]
Debt Instrument [Line Items]
Participation fees for letters of credit	0.625%
Letters of Credit [Member]
Debt Instrument [Line Items]
Amount available for general purposes	$ 250,000,000
Letters of Credit [Member] | Minimum [Member]
Debt Instrument [Line Items]
Participation fees for letters of credit	0.75%
Letters of Credit [Member] | Maximum [Member]
Debt Instrument [Line Items]
Participation fees for letters of credit	1.25%
Senior Unsecured Credit Facilities [Member]
Debt Instrument [Line Items]
Maturity period of Credit agreement	Sep. 28, 2018