Earnings per Share (Details) $ / shares in Units, $ in Thousands			3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 14, 2019	Jun. 13, 2019	Jun. 30, 2020 USD ($) $ / shares shares	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($) $ / shares shares	Mar. 31, 2019 USD ($)	Jun. 30, 2020 USD ($) $ / shares shares	Jun. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Reverse stock split, ratio of shares surrendered to shares received	15	15
Numerator:
Net income (loss) | $			$ 1,114	$ (20,145)	$ (7,748)	$ (5,275)	$ (19,031)	$ (13,023)	$ (61,100)	$ (122,100)	$ (210,100)
Denominator:
Weighted-average shares used to compute net income (loss) per share attributable to common stockholders-basic			13,432,872		13,034,913		13,369,338	13,007,558
Weighted average diluted shares outstanding (in shares)			13,999,755		13,034,913		13,369,338	13,007,558
Net income (loss) per share attributable to common stockholders-basic | $ / shares			$ 0.08		$ (0.59)		$ (1.42)	$ (1.00)
Net income (loss) per share attributable to common stockholders-diluted | $ / shares			$ 0.08		$ (0.59)		$ (1.42)	$ (1.00)
Class A
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, outstanding (in shares)			9,886,644				9,886,644		7,799,093
Numerator:
Net income (loss) | $			$ 811		$ (3,927)		$ (13,242)	$ (6,159)
Net income (loss) attributable to common stockholders | $			$ 811		$ (3,927)		$ (13,242)	$ (6,159)
Denominator:
Weighted-average shares used to compute net income (loss) per share attributable to common stockholders-basic			9,778,697		6,607,221		9,302,406	6,152,131
Effect of dilutive securities:			566,883
Weighted average diluted shares outstanding (in shares)			10,345,580		6,607,221		9,302,406	6,152,131
Net income (loss) per share attributable to common stockholders-basic | $ / shares			$ 0.08		$ (0.59)		$ (1.42)	$ (1.00)
Net income (loss) per share attributable to common stockholders-diluted | $ / shares			$ 0.08		$ (0.59)		$ (1.42)	$ (1.00)
Class B
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, outstanding (in shares)			3,654,147				3,654,147		5,464,196
Numerator:
Net income (loss) | $			$ 303		$ (3,821)		$ (5,789)	$ (6,864)
Net income (loss) attributable to common stockholders | $			$ 303		$ (3,821)		$ (5,789)	$ (6,864)
Denominator:
Weighted-average shares used to compute net income (loss) per share attributable to common stockholders-basic			3,654,175		6,427,692		4,066,932	6,855,427
Weighted average diluted shares outstanding (in shares)			3,654,175		6,427,692		4,066,932	6,855,427
Net income (loss) per share attributable to common stockholders-basic | $ / shares			$ 0.08		$ (0.59)		$ (1.42)	$ (1.00)
Net income (loss) per share attributable to common stockholders-diluted | $ / shares			$ 0.08		$ (0.59)		$ (1.42)	$ (1.00)
Class C
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, outstanding (in shares)			0				0		0