Fair Value Measurements and Derivative Instruments (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign Currency Derivative Liabilities at Fair Value	$ 1,000,000
Foreign Currency Derivative Assets at Fair Value	1,000,000
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds / commercial paper	581,648,000	239,157,000
Equity securities	0	0
Commingled fixed income securities	0	0
Debt securities - U.S. and foreign governments, agencies and municipalities	124,221,000	93,175,000
Debt securities - corporate	0	0
Mortgage-back / asset-back securities	0	0
Interest rate swaps	0	0
Foreign exchange contracts	0	0
Total assets	705,869,000	332,332,000
Foreign exchange contracts	0	0
Total liabilities	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds / commercial paper	34,369,000	300,702,000
Equity securities	25,106,000	22,097,000
Commingled fixed income securities	29,359,000	27,747,000
Debt securities - U.S. and foreign governments, agencies and municipalities	18,908,000	19,042,000
Debt securities - corporate	43,926,000	31,467,000
Mortgage-back / asset-back securities	162,375,000	134,262,000
Interest rate swaps	10,117,000	15,465,000
Foreign exchange contracts	2,582,000	4,230,000
Total assets	326,742,000	555,012,000
Foreign exchange contracts	(1,174,000)	(1,439,000)
Total liabilities	(1,174,000)	(1,439,000)
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds / commercial paper	0	0
Equity securities	0	0
Commingled fixed income securities	0	0
Debt securities - U.S. and foreign governments, agencies and municipalities	0	0
Debt securities - corporate	0	0
Mortgage-back / asset-back securities	0	0
Interest rate swaps	0	0
Foreign exchange contracts	0	0
Total assets	0	0
Foreign exchange contracts	0	0
Total liabilities	0	0
Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds / commercial paper	616,017,000	539,859,000
Equity securities	25,106,000	22,097,000
Commingled fixed income securities	29,359,000	27,747,000
Debt securities - U.S. and foreign governments, agencies and municipalities	143,129,000	112,217,000
Debt securities - corporate	43,926,000	31,467,000
Mortgage-back / asset-back securities	162,375,000	134,262,000
Interest rate swaps	10,117,000	15,465,000
Foreign exchange contracts	2,582,000	4,230,000
Total assets	1,032,611,000	887,344,000
Foreign exchange contracts	(1,174,000)	(1,439,000)
Total liabilities	(1,174,000)	(1,439,000)
Carrying value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	(4,017,375,000)	(4,233,909,000)
Fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ (4,200,970,000)	$ (4,364,176,000)