CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE EARNINGS (LOSS) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net earnings (loss)		$ 638.1	$ (19.9)
Other comprehensive earnings (loss), net of tax:
Unrealized gain (loss) on investments and other financial instruments, net (excluding investments in unconsolidated affiliates)	[1]	5.3	(0.2)
Unrealized (loss) gain relating to investments in unconsolidated affiliates	[2]	(3.9)	5.9
Reclassification adjustments for unrealized gains and losses on unconsolidated affiliates, net of tax, included in net earnings	[3]	44.3	0.6
Other comprehensive earnings		45.7	6.3
Comprehensive earnings (loss)		683.8	(13.6)
Less: Comprehensive loss attributable to noncontrolling interests		(9.6)	(3.1)
Comprehensive earnings (loss) attributable to Cannae Holdings, Inc.		693.4	(10.5)
Unrealized gain (loss) on investments and other financial instruments, income tax expense (benefit)		1.4	(0.1)
Unrealized (loss) gain relating to investments in unconsolidated affiliates, income tax (benefit) expense		(1.0)	1.6
Reclassification adjustments for unrealized gains and losses on unconsolidated affiliates, tax expense		$ 11.8	$ 0.2

[1] Net of income tax expense (benefit) of $1.4 million and $(0.1) million for the three months ended March 31, 2020 and 2019, respectively.

[2] Net of income tax (benefit) expense of $(1.0) million and $1.6 million for the three months ended March 31, 2020 and 2019, respectively.

[3] Net of income tax expense of $11.8 million and $0.2 million for the three months ended March 31, 2020 and 2019, respectively