Summary of Significant Accounting Policies - (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Item Effected [Line Items]
Selling, general and administrative expenses	$ 270,768	$ 252,107	$ 534,129	$ 505,102
Non-operating expenses	$ 7,527	6,299	$ 15,013	12,146
As Reported
Item Effected [Line Items]
Selling, general and administrative expenses		257,338		515,383
Non-operating expenses		1,068		1,865
Reclassification
Item Effected [Line Items]
Selling, general and administrative expenses		(5,231)		(10,281)
Non-operating expenses		$ 5,231		$ 10,281