Credit Facility and Long-Term Debt (Details 2) (USD $)	0 Months Ended		12 Months Ended
	Oct. 29, 2013	May 08, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Carrying amount			$ 1,491,466,000	$ 500,000,000
Proceeds from Issuance of Long-term Debt	991,800,000	499,200,000	991,786,000	500,000,000	0
Debt Instrument, Unamortized Discount	(8,200,000)	(800,000)
Debt Issuance Cost	5,500,000	3,700,000
Senior Notes [Member] | Two Point Five Percent Senior Note Maturing November 15, 2018 [Member]
Debt Instrument [Line Items]
Due Date	Nov. 15, 2018
Coupon rate	2.50%
Effective interest rate	2.71%
Principal Amount	600,000,000		600,000,000	0
Carrying amount			596,920,000	0
Debt Instrument, Unamortized Discount			(3,080,000)	0
Debt Instrument, Fair Value Disclosure			598,836,000	0
Senior Notes [Member] | Four Point One Percent Senior Note Maturing November 15, 2023 [Member]
Debt Instrument [Line Items]
Due Date	Nov. 15, 2023
Coupon rate	4.10%
Effective interest rate	4.29%
Principal Amount	400,000,000		400,000,000	0
Carrying amount			395,056,000	0
Debt Instrument, Unamortized Discount			(4,944,000)	0
Debt Instrument, Fair Value Disclosure			392,680,000	0
Senior Notes [Member] | One Point Seven Five Percent Senior Note Maturing May 15, 2017 [Member]
Debt Instrument [Line Items]
Due Date		May 15, 2017
Coupon rate		1.75%
Effective interest rate		1.94%
Principal Amount		500,000,000	500,000,000	500,000,000
Carrying amount			499,490,000	500,000,000
Debt Instrument, Unamortized Discount			(510,000)	0
Debt Instrument, Fair Value Disclosure			$ 501,310,000	$ 512,200,000