Fair Value Measurements and Derivative Instruments (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Net	$ 1,000,000	$ 1,000,000
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	312,557,000
Liabilities:	0
Money market funds / commercial paper		581,648,000
Equity securities		0
Commingled fixed income securities		0
Debt securities - U.S. and foreign governments, agencies and municipalities		124,221,000
Debt securities - corporate		0
Mortgage-back / asset-back securities		0
Interest rate swaps		0
Foreign exchange contracts		0
Total assets		705,869,000
Foreign exchange contracts		0
Total liabilities		0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	411,998,000
Liabilities:	(5,473,000)
Money market funds / commercial paper		34,369,000
Equity securities		25,106,000
Commingled fixed income securities		29,359,000
Debt securities - U.S. and foreign governments, agencies and municipalities		18,908,000
Debt securities - corporate		43,926,000
Mortgage-back / asset-back securities		162,375,000
Interest rate swaps		10,117,000
Foreign exchange contracts		2,582,000
Total assets		326,742,000
Foreign exchange contracts		(1,174,000)
Total liabilities		(1,174,000)
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Liabilities:	0
Money market funds / commercial paper		0
Equity securities		0
Commingled fixed income securities		0
Debt securities - U.S. and foreign governments, agencies and municipalities		0
Debt securities - corporate		0
Mortgage-back / asset-back securities		0
Interest rate swaps		0
Foreign exchange contracts		0
Total assets		0
Foreign exchange contracts		0
Total liabilities		0
Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	724,555,000
Liabilities:	(5,473,000)
Money market funds / commercial paper		616,017,000
Equity securities		25,106,000
Commingled fixed income securities		29,359,000
Debt securities - U.S. and foreign governments, agencies and municipalities		143,129,000
Debt securities - corporate		43,926,000
Mortgage-back / asset-back securities		162,375,000
Interest rate swaps		10,117,000
Foreign exchange contracts		2,582,000
Total assets		1,032,611,000
Foreign exchange contracts		(1,174,000)
Total liabilities		(1,174,000)
Carrying value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	(3,650,590,000)	(4,017,375,000)
Fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	(3,867,130,000)	(4,200,970,000)
Money market funds / commercial paper | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	194,486,000
Money market funds / commercial paper | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	147,259,000
Money market funds / commercial paper | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Money market funds / commercial paper | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	341,745,000
Equity securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Equity securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	25,384,000
Equity securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Equity securities | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	25,384,000
Commingled fixed income securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Commingled fixed income securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	26,772,000
Commingled fixed income securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Commingled fixed income securities | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	26,772,000
Debt securities - U.S. and foreign governments, agencies and municipalities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	118,071,000
Debt securities - U.S. and foreign governments, agencies and municipalities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	18,049,000
Debt securities - U.S. and foreign governments, agencies and municipalities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Debt securities - U.S. and foreign governments, agencies and municipalities | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	136,120,000
Debt securities - corporate | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Debt securities - corporate | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	31,534,000
Debt securities - corporate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Debt securities - corporate | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	31,534,000
Mortgage-backed / asset-backed securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Mortgage-backed / asset-backed securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	159,300,000
Mortgage-backed / asset-backed securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Mortgage-backed / asset-backed securities | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	159,300,000
Interest rate swaps | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Interest rate swaps | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	1,855,000
Interest rate swaps | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Interest rate swaps | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	1,855,000
Foreign exchange contracts | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Liabilities:	0
Foreign exchange contracts | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	1,845,000
Liabilities:	(5,473,000)
Foreign exchange contracts | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	0
Liabilities:	0
Foreign exchange contracts | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets:	1,845,000
Liabilities:	$ (5,473,000)