Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
In-transit revenue balance	$ 20,100	$ 15,600
Allowance for Doubtful Accounts Receivable, Current	$ 555,930	$ 616,830
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000	10,000
Preferred stock, shares issued (in shares)	0	0
Common Class A [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000	500,000
Common stock, shares issued (in shares)	173,066	172,844
Common stock, shares outstanding (in shares)	173,066	172,844