Employee Benefit Plans - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Other selling and administrative expenses	$ 360,000	$ 353,296	$ 784,617	$ 684,125
Other non-operating expense, net	3,063	5,128	2,455	5,622
Cash contributions made during the period			17,000
Expected additional cash contributions	$ 4,000		$ 4,000
Accounting Standards Update 2017-07
Defined Benefit Plan Disclosure [Line Items]
Other selling and administrative expenses		300		(1,100)
Other non-operating expense, net		$ (300)		$ 1,100