Summary of Significant Accounting Policies - Company's Accounts Receivable and Securitized Accounts Receivable (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivables	$ 2,277,042	$ 1,825,515
Gross domestic securitized accounts receivable	811,000	591,000
Less allowance for doubtful accounts	(46,031)	(32,506)	$ (21,903)	$ (23,842)
Net accounts and securitized accounts receivable	2,231,011	1,793,009
Accounts Receivable Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivables	661,677	529,885
Accounts Receivable Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivables	$ 804,365	$ 704,630