Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Collected on sold receivables			$ 91,142	$ 59,286
Increase to earnings reinvested in the business			1,463,976		$ 1,414,485
Increase to deferred tax assets			11,259		7,885
(Decrease) to prepaid expense and other current assets			(53,926)		(43,206)
(Decrease) to deferred tax liabilities			(31,714)		$ (18,724)
ASU 2016-15 [Member]
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Collected on sold receivables	$ 35,000	$ 25,000	$ 91,142	$ 59,286
ASU 2016-16 [Member]
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Increase to earnings reinvested in the business	400
Increase to deferred tax assets	3,000
(Decrease) to prepaid expense and other current assets	(3,700)
(Decrease) to deferred tax liabilities	$ (1,100)