Reinsurance Activity - Coverage (Details)					12 Months Ended
	Jan. 01, 2016 USD ($)	Jul. 01, 2015	Jan. 01, 2014	Jul. 01, 2013 USD ($)	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($) item	Dec. 31, 2013 USD ($) item
Multi-line excess of loss coverage
Reinsurance activity
Loss amount covered under reinsurance contract					$ 500,000
Reinsurance retention amount					500,000
Catastrophic coverage | First layer of protection
Reinsurance activity
Loss amount covered under reinsurance contract					17,000,000
Reinsurance retention amount					8,000,000
Catastrophic coverage | Second layer of protection
Reinsurance activity
Loss amount covered under reinsurance contract					25,000,000
Reinsurance coverage in losses per event					25,000,000
Catastrophic coverage | Third layer of protection
Reinsurance activity
Loss amount covered under reinsurance contract					25,000,000
Reinsurance coverage in losses per event					50,000,000
Catastrophic coverage | Fourth layer of protection
Reinsurance activity
Loss amount covered under reinsurance contract					50,000,000
Reinsurance coverage in losses per event					75,000,000
ASIC | Catastrophic coverage
Reinsurance activity
Loss amount covered under reinsurance contract					6,500,000
Reinsurance retention amount					1,500,000
NLIC | Catastrophic coverage
Reinsurance activity
Reinsurance retention amount					8,000,000
NLC | Catastrophic coverage
Reinsurance activity
Loss amount covered under reinsurance contract	$ 1,000,000
Aggregate coverage in excess of retention for sub-catastrophic events	$ 10,000,000
Reinsurance retention amount					$ 8,000,000
Number of layers of protection under reinsurance | item					4
Participation retained (as a percent)					9.00%
Number of significant catastrophe experienced | item					0	0	2
Renewal period of reinsurance contract		2 years
Number of tornado, hail and wind storms experienced | item					11	8	2
Incurred losses					$ 35,300,000	$ 21,700,000	$ 18,300,000
Reinsurance recoverable favorable (loss)					$ 9,100,000	$ 1,800,000
Reinsurance recoverable subscription level					91.00%	66.00%
Reinstatement premiums					$ 200,000	$ 200,000	$ 300,000
NLC | Catastrophic coverage | Maximum
Reinsurance activity
Loss amount covered under reinsurance contract				$ 140,000,000
NLC | Catastrophic coverage | Fourth layer of protection
Reinsurance activity
Loss amount covered under reinsurance contract				100,000,000
Reinsurance coverage in losses per event				$ 40,000,000
NLC | Catastrophic coverage | Third and fourth layer of protection
Reinsurance activity
Renewal period of reinsurance contract				2 years
NLC | Catastrophic coverage | First and second layers of protection
Reinsurance activity
Renewal period of reinsurance contract			18 months
NLIC and ASIC | Catastrophic coverage | Maximum
Reinsurance activity
Reinsurance retention amount					$ 8,000,000