Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment reporting information
Earned insurance premiums	$ 3.0	$ 3.0
Net investment income	19.7	12.8
Net realized and unrealized investment gains	(53.7)	36.3
Advertising and commission revenues	71.0	33.8
Other revenue	2.1	2.9
Total revenues	42.1	88.8
Loss and loss adjustment expenses		1.1
Insurance acquisition expenses	1.4	1.3
Other underwriting expenses	0.1	0.1
Cost of sales	58.1	28.8
General and administrative expenses	47.9	60.7
Interest expense	0.6	0.4
Total expenses	108.1	92.4
Pre-tax income (loss)	(66.0)	(3.6)
HG Global-BAM
Segment reporting information
Advertising and commission revenues	0.0	0.0
Loss and loss adjustment expenses		0.0
Cost of sales	0.0	0.0
Interest expense	0.0	0.0
Pre-tax income (loss)	(14.3)	(5.6)
MediaAlpha
Segment reporting information
Earned insurance premiums	0.0	0.0
Net investment income	0.0	0.0
Net realized and unrealized investment gains	0.0	0.0
Advertising and commission revenues	70.1	32.5
Other revenue	1.6	0.0
Total revenues	71.7	32.5
Insurance acquisition expenses	0.0	0.0
Other underwriting expenses	0.0	0.0
Cost of sales	57.4	27.7
General and administrative expenses	14.1	5.6
Interest expense	0.4	0.2
Total expenses	71.9	33.5
Pre-tax income (loss)	$ (0.2)	$ (1.0)
Percentage of advertising revenue	31.00%	27.00%
Other Operations
Segment reporting information
Earned insurance premiums	$ 0.0	$ 1.0
Net investment income	16.0	10.2
Net realized and unrealized investment gains	(45.8)	35.0
Advertising and commission revenues	0.9	1.3
Other revenue	0.3	2.5
Total revenues	(28.6)	50.0
Loss and loss adjustment expenses		1.1
Insurance acquisition expenses	0.0	0.1
Other underwriting expenses	0.0	0.0
Cost of sales	0.7	1.1
General and administrative expenses	22.0	44.5
Interest expense	0.2	0.2
Total expenses	22.9	47.0
Pre-tax income (loss)	$ (51.5)	$ 3.0