Stockholder's Equity (Details) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($) class
Stockholders' Equity
Number of classes of common stock \| class	3
Class B common stock
Stockholders' Equity
Consideration for redemption of shares \| $	$ 0

Equity impact of the value of stock bought back by the entity at the exercise price or redemption price.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Name:	us-gaap_StockRedeemedOrCalledDuringPeriodValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration