Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Income before income tax expense		$ 42,410	$ 38,593	$ 61,014	$ 60,604
Less: Net income attributable to GS Holdings prior to the Reorganization Transactions		19,609		38,213
Less: Net income attributable to noncontrolling interests subsequent to the Reorganization Transactions		15,657		15,657
Income tax expense		1,594	$ 0	1,594	$ 0
Net income attributable to GreenSky, Inc. - basic		5,550		5,550
Less: Income tax expense on reallocation of net income attributable to noncontrolling interests (1)		3,493		3,493
Net income attributable to GreenSky, Inc. - diluted		$ 17,714		$ 17,714
Denominator:
Weighted average shares of Class A common stock outstanding - basic (in shares)		57,399,632		57,399,632
Add: Dilutive effects as shown separately below
Holdco warrants exchangeable for Class A common stock (in shares)		563,458		563,458
Weighted average shares of Class A common stock outstanding - diluted (in shares)		188,889,922		188,889,922
Earnings per share of Class A common stock outstanding - basic (in dollars per share)	[1]	$ 0.10		$ 0.10
Earnings per share of Class A common stock outstanding - diluted (in dollars per share)	[1]	$ 0.09		$ 0.09
Effective income tax rate (as a percent)		22.30%		22.30%
Antidilutive securities excluded from computation of earnings per share (in shares)		472,500		472,500
HoldCo Units
Add: Dilutive effects as shown separately below
Holdco Units that are exchangeable for Class A common stock (in shares)		128,257,580		128,257,580
Class A common stock
Add: Dilutive effects as shown separately below
Dilutive effect of share based compensation awards (in shares)		2,479,889		2,479,889
Unvested Class A stock awards
Add: Dilutive effects as shown separately below
Dilutive effect of share based compensation awards (in shares)		189,363		189,363

[1] Basic and diluted earnings per share of Class A common stock is applicable only for the period from May 24, 2018 through June 30, 2018, which is the period following the initial public offering ("IPO") and related Reorganization Transactions (as defined in Note 1 to the unaudited consolidated financial statements). See Note 2, Earnings per Share for the number of shares used in the computation of earnings per share of Class A common stock and the basis for the computation of earnings per share.