SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
SUPPLEMENTARY INSURANCE INFORMATION
Net investment income	$ 56.0	$ 32.1	$ 10.9
HG Global BAM
SUPPLEMENTARY INSURANCE INFORMATION
Deferred acquisition costs	14.8	10.6	6.9
Future policy benefits, losses, claims and loss expenses	0.0	0.0	0.0
Unearned premiums	136.8	82.9	50.2
Other policy claims and benefits payable	0.0	0.0	0.0
Premiums earned	9.4	5.9	3.3
Net investment income	12.3	9.0	6.1
Benefits, claims, losses, and settlement expenses	0.0	0.0	0.0
Amortization of deferred policy acquisition costs	4.0	3.4	2.9
Other operating expenses	0.4	0.4	0.4
Premiums written	63.2	38.6	25.9
Other Operations
SUPPLEMENTARY INSURANCE INFORMATION
Deferred acquisition costs	0.0	0.0	0.0
Future policy benefits, losses, claims and loss expenses	0.0	0.0	0.0
Unearned premiums	0.0	0.0	0.0
Other policy claims and benefits payable	0.0	0.0	0.0
Premiums earned	1.0	7.5	8.7
Net investment income	0.0	0.2	0.2
Benefits, claims, losses, and settlement expenses	1.1	8.0	8.2
Amortization of deferred policy acquisition costs	0.1	2.2	3.4
Other operating expenses	0.0	0.1	0.0
Premiums written	0.9	6.5	10.1
Non-insurance | Operating Segments
SUPPLEMENTARY INSURANCE INFORMATION
Net investment income	$ 43.7	$ 22.9	$ 4.6