3. Fair Value and Gross Unrealized Losses with Unrealized Losses (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 0.2	$ 0.4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.0	0.1
Debt Securities, Available-for-sale, Unrealized Loss Position	35.9	111.8
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	35.9	91.9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0.0	19.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0.2	0.3
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.1	0.1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.0	0.0
Debt Securities, Available-for-sale, Unrealized Loss Position	23.2	48.6
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	23.2	46.5
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0.0	2.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0.1	0.1
US Government Sponsored Agencies [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax		0.2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0.0
Debt Securities, Available-for-sale, Unrealized Loss Position		38.3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		27.5
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		10.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		0.2
Asset-backed Securities [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0.1	0.1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.0	0.1
Debt Securities, Available-for-sale, Unrealized Loss Position	12.7	24.9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	12.7	17.9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0.0	7.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0.1	$ 0.0
Fair Value, Recurring [Member] | Debt Securities [Member]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 0.2