Consolidated Balance Sheets Parenthetical - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts		$ 4,461	$ 4,814
Preferred stock par value (usd per share)		$ 0.001	$ 0.001
Preferred stock authorized for issuance, shares		40,000,000	40,000,000
Preferred stock, shares issued		0	0
Preferred stock, shares outstanding		0	0
Treasury stock issued, shares		14,102,185	14,102,185
Assets	[1]	$ 8,251,391	$ 8,169,328
Liabilities	[1]	$ 4,728,294	$ 4,952,148
Common Class A
Common stock par value (usd per share)		$ 0.001	$ 0.001
Common stock authorized for issuance, shares		1,000,000,000	1,000,000,000
Common stock issued, shares		101,790,837	101,429,999
Common stock outstanding, shares		87,688,652	87,327,814
Common Class B
Common stock par value (usd per share)		$ 0.001	$ 0.001
Common stock authorized for issuance, shares		1,000,000,000	1,000,000,000
Common stock issued, shares		5,557	5,557
Common stock outstanding, shares		5,557	5,557
Senior Secured Credit Agreement | Term Loan Facility
Debt instrument, unamortized discount and debt issuance costs		$ 20,000	$ 24,000
Noncurrent | Senior Secured Credit Agreement | Term Loan Facility
Debt instrument, unamortized discount and debt issuance costs		29,434	36,332
Variable Interest Entity, Primary Beneficiary
Assets		73,000	81,000
Liabilities		$ 28,000	$ 29,000

[1] The Company’s consolidated total assets as of December 31, 2018 and December 31, 2017 include total assets of variable interest entities (“VIEs”) of $73 million and $81 million, respectively, which can only be used to settle the obligations of the VIEs. The Company’s consolidated total liabilities as of December 31, 2018 and December 31, 2017 include total liabilities of the VIEs of $28 million and $29 million, respectively, for which the creditors of the VIEs have no recourse to the Company (see Note 1).