2. Fair Value and Gross Unrealized Losses with Unrealized Losses (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Price Change Debt Security	5.00%
Tolerable variance Level 2 debt security pricing	1.00%
Fair Value of Investments with Gross Unrealized Losses in loss position 12 months or more	$ 36.9	$ 43.9
Cost Method Investment, Percentage Owned	37.00%
Fair Value of Investments with Gross Unrealized Losses in loss position less than 12 months	$ 199.4	168.7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0.9
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0.7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 2.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		$ 0.8