Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Allowance for Doubtful Accounts		$ 4,718	$ 4,461
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]	$ 8,420,134	$ 8,251,391
Liabilities	[1]	$ 4,794,369	$ 4,728,294
Class A Common Stock
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		102,349,311	101,790,837
Common stock outstanding, shares		88,247,126	87,688,652
Class B Common Stock
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		$ 19,000	$ 20,000
Noncurrent | Senior Secured Credit Agreement | Term Loan Facility
Debt instrument, unamortized discount and debt issuance costs		27,726	29,434
Variable Interest Entity, Primary Beneficiary
Assets		69,000	73,000
Liabilities		$ 27,000	$ 28,000

[1] (1) The Company’s consolidated total assets as of March 31, 2019 and December 31, 2018 include total assets of variable interest entities (“VIEs”) of $69 million and $73 million, respectively, which can only be used to settle the obligations of the VIEs. The Company’s consolidated total liabilities as of March 31, 2019 and December 31, 2018 include total liabilities of the VIEs of $27 million and $28 million, respectively, for which the creditors of the VIEs have no recourse to the Company (see Note 1).