Earnings per Share (Schedule of Calculations of Basic and Diluted 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
Basic earnings per common share:
Net income attributable to NI Holdings, Inc.	$ 226	$ 129	$ 6,348	$ 4,818
Weighted average shares outstanding	22,377,421	22,663,280	22,369,632	22,711,373
Basic earnings per common share	$ 0.01	$ 0.01	$ 0.28	$ 0.21
Numerator:
Net income attributable to NI Holdings, Inc.	$ 226	$ 129	$ 6,348	$ 4,818
Denominator:
Number of shares used in basic computation	22,377,421	22,663,280	22,369,632	22,711,373
Weighted average effect of dilutive securities
Add: Restricted stock units and performance share units	19,537		15,939
Number of shares used in per share computations	22,396,958	22,663,280	22,385,571	22,711,373
Diluted earnings per common share	$ 0.01	$ 0.01	$ 0.28	$ 0.21