Other Receivables (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other receivables	$ 372,919	$ 288,156
Supplier rebates and non-trade receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other receivables	268,949	183,498
Medicare bad debt claims
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other receivables	$ 103,970	$ 104,658