Debt - LT Debt (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 27, 2014	Sep. 28, 2013	Sep. 27, 2014	Sep. 28, 2013	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term debt	$ 2,211,037		$ 2,211,037		$ 2,226,132
Net proceeds from note offering			0	591,156
Loss on prepayment of debt	0	0	0	4,277
Loss on prepayment of debt, net of tax				2,627
Loss on prepayment of debt, net of tax per share on a basic basis				$ 0.03
Loss on prepayment of debt, net of tax per share on a diluted basis				$ 0.03
Accounts receivable, net	5,060,959		5,060,959		5,769,759
Investment Income, Interest and Dividend	2,369	3,272	3,898	4,392
Revolving Credit Facility due in 2018 [Member]
Debt Instrument [Line Items]
Long-term debt	49,800		49,800		0
Debt Instrument, Basis Spread on Variable Rate	1.30%
Debt Instrument, Interest Rate, Effective Percentage	1.40%		1.40%
Line of Credit Facility, Commitment Fee Percentage	0.20%
Line of Credit Facility, Maximum Borrowing Capacity	1,500,000		1,500,000
Asset securitization program [Member]
Debt Instrument [Line Items]
Long-term debt	360,000		360,000		420,000
Debt Instrument, Interest Rate, Effective Percentage	0.62%		0.62%
Asset Securitization Program Prior Maximum Capacity	775,000		775,000
Asset Securitization Program Maximum Capacity	900,000		900,000
Asset Securitization Program Interest Rate Spread At End of Period	0.40%		0.40%
Asset Securitization Program Facility Fee	0.40%		0.40%
Accounts receivable, net	1,543,118		1,543,118		1,867,552
Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Prior Maximum Borrowing Capacity	70,000		70,000
Line of Credit Facility, Maximum Borrowing Capacity	100,000		100,000
6.875% senior notes, due 2013 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.875%		6.875%
Redemption of Senior Notes, principal amount				332,107
3.375% notes, due 2015 [Member]
Debt Instrument [Line Items]
Long-term debt	252,957		252,957		255,004
Debt Instrument, Interest Rate, Stated Percentage	3.375%		3.375%
Debt Instrument, Fair Value	255,000		255,000		260,000
Senior Debentures Due in 2018 [Member]
Debt Instrument [Line Items]
Long-term debt	199,235		199,235		199,078
Debt Instrument, Interest Rate, Stated Percentage	6.875%		6.875%
Debt Instrument, Fair Value	228,000		228,000		228,000
3.00% notes, due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt	298,914		298,914		298,691
Debt Instrument, Interest Rate, Stated Percentage	3.00%		3.00%
Debt Instrument, Fair Value	309,000		309,000		300,000
Principal Amount of Issuance of Long-term Debt				300,000
6.00% notes, due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt	299,951		299,951		299,945
Debt Instrument, Interest Rate, Stated Percentage	6.00%		6.00%
Debt Instrument, Fair Value	339,000		339,000		330,000
5.125% notes, due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt	249,494		249,494		249,435
Debt Instrument, Interest Rate, Stated Percentage	5.125%		5.125%
Debt Instrument, Fair Value	270,000		270,000		260,000
4.50% notes, due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt	297,913		297,913		297,767
Debt Instrument, Interest Rate, Stated Percentage	4.50%		4.50%
Debt Instrument, Fair Value	309,000		309,000		291,000
Principal Amount of Issuance of Long-term Debt				300,000
7.5% senior debentures, due 2027 [Member]
Debt Instrument [Line Items]
Long-term debt	198,275		198,275		198,170
Debt Instrument, Interest Rate, Stated Percentage	7.50%		7.50%
Debt Instrument, Fair Value	242,000		242,000		232,000
Interest rate swaps designated as fair value hedges [Member]
Debt Instrument [Line Items]
Long-term debt	(579)		(579)		0
Other obligations with various interest rates and due dates [Member]
Debt Instrument [Line Items]
Long-term debt	$ 5,077		$ 5,077		$ 8,042