Subsequent Events - Authorized Shares and Reverse Stock Split (Additional Information) (Details)	Jul. 19, 2018 shares	Jul. 07, 2018	Jun. 30, 2018 shares	Dec. 31, 2017 shares
Subsequent Event [Line Items]
Common stock, authorized (in shares)			113,333,333	113,333,333
Subsequent Event
Subsequent Event [Line Items]
Reverse stock split, conversion ratio		0.6667
Class A common stock
Subsequent Event [Line Items]
Common stock, authorized (in shares)			600,000,000
Class A common stock | Subsequent Event
Subsequent Event [Line Items]
Common stock, authorized (in shares)	400,000,000
Class B common stock
Subsequent Event [Line Items]
Common stock, authorized (in shares)			600,000
Class B common stock | Subsequent Event
Subsequent Event [Line Items]
Common stock, authorized (in shares)	400,000
Reverse stock split, conversion ratio	0.6667