Accounts payable and accrued expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Outstanding checks in excess of cash	$ 7,325	$ 8,879
Accounts payable, trade	951,200	810,034
Accrued expenses	384,147	363,919
Product warranties	38,973	39,035
Accrued interest	16,725	22,363
Accrued compensation and benefits	191,191	207,442
Total accounts payable and accrued expenses	$ 1,589,561	$ 1,451,672