Accounts payable and accrued expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Outstanding checks in excess of cash	$ 1,974	$ 8,879
Accounts payable, trade	897,525	810,034
Accrued expenses	334,879	363,919
Product warranties	40,456	39,035
Accrued interest	8,155	22,363
Accrued compensation and benefits	181,004	207,442
Total accounts payable and accrued expenses	$ 1,463,993	$ 1,451,672