Employee Benefit Plans - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Other selling and administrative expenses	$ 325,874	$ 381,214	$ 1,110,491	$ 1,065,339
Other non-operating expense, net	1,911	1,910	4,366	7,532
Cash contributions made during the period			17,000
Expected additional cash contributions	$ 3,000		$ 3,000
Accounting Standards Update 2017-07
Defined Benefit Plan Disclosure [Line Items]
Other selling and administrative expenses		(500)		(1,600)
Other non-operating expense, net		$ 500		$ 1,600