LT Debt (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments [Text Block]

Long-term debt consists of the following at December 31:

	2017		2016
Asset securitization program	$	490,000	$	460,000
6.875% senior debentures, due 2018	—		199,348
3.00% notes, due 2018	—		299,013
6.00% notes, due 2020	208,971		299,183
5.125% notes, due 2021	130,400		248,843
3.50% notes, due 2022	346,518		345,776
4.50% notes, due 2023	297,122		296,646
3.25% notes, due 2024	493,161		—
4.00% notes, due 2025	345,182		344,625
7.50% senior debentures, due 2027	109,694		198,514
3.875% notes, due 2028	493,563		—
Other obligations with various interest rates and due dates	18,434		4,386
	$	2,933,045	$	2,696,334

Schedule of Fair Value of Debt [Text Block]

The estimated fair market value of long-term debt at December 31, using quoted market prices, is as follows:

	2017		2016
6.875% senior debentures, due 2018	$	—	$	212,500
3.00% notes, due 2018	300,500		303,500
6.00% notes, due 2020	224,000		325,500
5.125% notes, due 2021	139,000		265,500
3.50% notes, due 2022	355,000		349,500
4.50% notes, due 2023	315,500		305,500
3.25% notes, due 2024	491,000		—
4.00% notes, due 2025	356,500		345,000
7.50% senior debentures, due 2027	138,500		238,000
3.875% notes, due 2028	501,000		—