Borrowings (Details)	12 Months Ended					12 Months Ended		12 Months Ended					12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended						12 Months Ended					12 Months Ended
	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2014 Note due 2015 [Member] USD ($)	Dec. 31, 2013 Note due 2015 [Member] USD ($)	Dec. 31, 2014 Note due 2018 [Member] USD ($)	Dec. 31, 2013 Note due 2018 [Member] USD ($)	Dec. 31, 2014 Note due 2020 [Member] USD ($)	Dec. 31, 2014 Note due 2020 [Member] EUR (€)	Dec. 31, 2013 Note due 2020 [Member] USD ($)	Dec. 31, 2014 Note due 2021 [Member] USD ($)	Dec. 31, 2013 Note due 2021 [Member] USD ($)	Dec. 31, 2014 Note due 2038 [Member] USD ($)	Dec. 31, 2013 Note due 2038 [Member] USD ($)	Dec. 31, 2014 Note due 2041 [Member] USD ($)	Dec. 31, 2013 Note due 2041 [Member] USD ($)	Dec. 31, 2014 Debentures due 2028 [Member] USD ($)	Dec. 31, 2013 Debentures due 2028 [Member] USD ($)	Dec. 31, 2014 Debenture due 2035 [Member] USD ($)	Dec. 31, 2013 Debenture due 2035 [Member] USD ($)	Dec. 31, 2014 Other long term debt instruments [Member] USD ($)	Dec. 31, 2013 Other long term debt instruments [Member] USD ($)	Dec. 31, 2014 Commercial Paper [Member]	Dec. 31, 2013 Commercial Paper [Member]	Dec. 31, 2014 Credit Agreement [Member] USD ($)	Dec. 31, 2014 Debentures [Member] USD ($)	Dec. 31, 2013 Debentures [Member] USD ($)	Dec. 31, 2014 Long-term Notes [Member] USD ($)	Dec. 31, 2013 Long-term Notes [Member] USD ($)	Dec. 31, 2014 Minimum [Member]	Dec. 31, 2014 Maximum [Member]
Letters of Credit [Abstract]
Letters of credit outstanding	$ 135,452,000
Maturities of Long-term Debt [Abstract]
2015	299,956,000
2016	114,000
2017	117,000
2018	348,958,000
2019	0
2020 and thereafter	1,903,852,000
Interest expense and interest income [Abstract]
Interest expense	131,689,000	124,535,000	125,992,000
Interest income	(4,510,000)	(3,881,000)	(4,723,000)
Interest expense, net	127,179,000	120,654,000	121,269,000
Short-term borrowings [Abstract]
Current installments	299,956,000	2,778,000
Commercial paper	478,000,000	226,500,000
Total short-term debt	777,956,000	229,278,000
Short-term Debt, Weighted Average Interest Rate																							0.10%	0.10%
Long-term borrowings [Abstract]
Long-term debt	2,552,997,000	2,601,979,000		299,836,000	299,638,000	348,928,000	348,598,000	363,970,000		411,500,000	449,839,000	449,813,000	247,948,000	247,859,000	345,830,000	345,671,000	199,517,000	199,483,000	296,685,000	296,526,000	444,000	2,891,000
Debt instrument, stated interest rate (in hundredths)				4.875%		5.45%		2.125%	2.125%		4.30%		6.60%		5.375%		6.65%		5.375%
Term of debt instrument (in years)				10 years		10 years		7 years	7 years		10 years		30 years		30 years		30 years		30 years
Debt instruments, maturity date				Oct. 15, 2015		Mar. 15, 2018		Dec. 01, 2020	Dec. 01, 2020		Mar. 01, 2021		Mar. 15, 2038		Mar. 01, 2041		Jun. 01, 2028		Oct. 15, 2035
Face amount of notes				300,000,000					300,000,000
Unamortized discount																										3,798,000	3,991,000	8,213,000	9,196,000
Proceeds from long-term debt, net of discount and issuance costs	0	403,776,000	0							403,776,000
Total long-term debt	2,253,041,000	2,599,201,000
Line of Credit Facility [Abstract]
Unsecured revolving credit facility, maximum borrowing capacity																									$ 1,000,000,000
Credit facility expiration date																									Nov. 10, 2016					Dec. 31, 2015	Dec. 31, 2020
Line of credit facility, interest rate description	At the Company's election, loans under the Credit Agreement will bear interest at a Eurodollar or Sterling rate based on LIBOR, plus an applicable margin ranging from 0.565% to 1.225% (subject to adjustment based on the credit rating accorded the Company's senior unsecured debt by S&P and Moody's), or at a base rate pursuant to a formula defined in the Credit Agreement.
Line of credit facility, covenant terms	the Credit Agreement requires the Company to pay a facility fee and imposes various restrictions on the Company such as, among other things, the requirement for the Company to maintain an interest coverage ratio of EBITDA to consolidated net interest expense of not less than 3.0 to 1
Line of credit facility, covenant compliance	The Company was in compliance with this covenant and its other long-term debt covenants at December 31, 2014 and had a coverage ratio of 12.7 to 1.