Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Allowance for Doubtful Accounts Receivable, Current	$ 3,277	$ 2,322
Accumulated depreciation	486,969	393,635
Accumulated amortization	$ 51,469	$ 39,018
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0
Preferred Stock, Shares Authorized	4,000	0
Preferred Stock, Shares Issued	0	0
Accounts Payable	$ 435,592	$ 367,307
Accrued Liabilities	106,045	81,104
Other Liabilities, Current	$ 4,242	$ 2,839
Common stock, $0.01 par value	$ 0.01	$ 0.01
Common stock shares authorized	100,000	100,000
Common stock shares issued	79,679	67,079
Treasury Stock, Common, Shares	1,018	980