Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Company's Accounts Receivable and Securitized Accounts Receivable

The Company’s accounts receivable and securitized accounts receivable include the following at December 31 (in thousands):

	2017			2016
Gross domestic accounts receivables	$	661,677		$	529,885
Gross domestic securitized accounts receivable	811,000			591,000
Gross foreign receivables	804,365			704,630
Total gross receivables	2,277,042			1,825,515
Less allowance for doubtful accounts	(46,031		)	(32,506		)
Net accounts and securitized accounts receivable	$	2,231,011		$	1,793,009

Allowance for Doubtful Accounts Related to Accounts Receivable

A rollforward of the Company’s allowance for doubtful accounts related to accounts receivable for the years ended December 31 is as follows (in thousands):

	2017			2016			2015
Allowance for doubtful accounts beginning of year	$	32,506		$	21,903		$	23,842
Provision for bad debts	44,857			35,885			24,629
Write-offs	(31,332		)	(25,282		)	(26,568		)
Allowance for doubtful accounts end of year	$	46,031		$	32,506		$	21,903