Fair Value (Details Textual) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended
	Jun. 30, 2013	Apr. 30, 2011	Jan. 30, 2016	Oct. 31, 2015	Jun. 03, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate principal amount of debt			$ 1,750,000	$ 875,000
Fair Value (Textual) [Abstract]
Cash and held to maturity investments			$ 70,100	76,400
3.0% Senior unsecured notes due April 15, 2016 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Frequency of Periodic Payment		semi-annual fixed interest payments due on April 15 and October 15 of each year, commencing October 15, 2011
Debt Instrument, Maturity Date		Apr. 15, 2016
2.875% Senior unsecured notes due June 1, 2023 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Frequency of Periodic Payment	semi-annual fixed interest payments due on June 1 and December 1 of each year, commencing December 1, 2013
Debt Instrument, Maturity Date	Jun. 01, 2023
3.9% Senior unsecured notes due December 15, 2025 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Frequency of Periodic Payment			semi-annual fixed interest payments due on June 15 and December 15 of each year, commencing June 15, 2016
Debt Instrument, Maturity Date	Dec. 15, 2025
5.3% Senior unsecured notes due December 15, 2045 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Frequency of Periodic Payment			semi-annual fixed interest payments due on June 15 and December 15 of each year, commencing June 15, 2016
Debt Instrument, Maturity Date			Dec. 15, 2045
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost of the Company's investments classified as available for sale			$ 3,400,000	2,600,000
Financial Instruments Not Recorded at Fair Value on a Recurring Basis [Member] | 3.0% Senior unsecured notes due April 15, 2016 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of the long-term debt				378,600
Aggregate principal amount of debt		$ 375,000
Interest rate to be paid on long term notes		3.00%
Financial Instruments Not Recorded at Fair Value on a Recurring Basis [Member] | 2.875% Senior unsecured notes due June 1, 2023 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of the long-term debt			485,300	$ 480,900
Aggregate principal amount of debt					$ 500,000
Interest rate to be paid on long term notes					2.875%
Financial Instruments Not Recorded at Fair Value on a Recurring Basis [Member] | 3.9% Senior unsecured notes due December 15, 2025 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of the long-term debt			876,700
Aggregate principal amount of debt					$ 850,000
Interest rate to be paid on long term notes					3.90%
Financial Instruments Not Recorded at Fair Value on a Recurring Basis [Member] | 5.3% Senior unsecured notes due December 15, 2045 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of the long-term debt			$ 421,700
Aggregate principal amount of debt					$ 400,000
Interest rate to be paid on long term notes					5.30%