Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
	Jan. 07, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2017	Nov. 17, 2016
Commitments and Contingencies Disclosure [Abstract]
Deferred rent			$ 1.5	$ 2.4
Total rent expense			14.7	$ 19.7	$ 16.0
Exposure to earthquake loss			66.2
Litigation settlement expense	$ 27.6
Payments for assessed penalty		$ 27.6
Penalty interest assessed, statutory rate							7.00%
Gain contingency, unrecorded amount			$ 31.1			$ 30.9