Fair Value Measurements - Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
FAIR VALUE MEASUREMENTS
Unamortized discount and debt issuance costs, net	$ 6,628	$ 7,395
Credit Agreement, dated March 6, 2018, Term Loan B
FAIR VALUE MEASUREMENTS
Unamortized discount and debt issuance costs, net	5,800	6,500
Credit Agreement, dated March 6, 2018, Term Loan B \| Carrying Value
FAIR VALUE MEASUREMENTS
Debt	488,600	491,100
Credit Agreement, dated March 6, 2018, Term Loan B \| Fair Value
FAIR VALUE MEASUREMENTS
Debt	488,000
Credit Agreement, dated March 6, 2018, Term Loan B \| Recurring basis \| Level 3 \| Fair Value
FAIR VALUE MEASUREMENTS
Debt	488,000
Credit Agreement, dated March 6, 2018, Term Loan B \| Revolving Credit Facility \| Recurring basis \| Level 3 \| Fair Value
FAIR VALUE MEASUREMENTS
Debt		489,900
Seller Notes \| Level 3 \| Carrying Value
FAIR VALUE MEASUREMENTS
Unamortized discount and debt issuance costs, net	800	900
Outstanding amount	$ 21,300	$ 14,600

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant