Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accrued earnouts	$ 4.1	$ 7.2
Performance targets, maximum potential obligation	5.8	10.2
Certificate of deposits		0.5
Treasury securities	0.2	0.2
Held-to-maturity investments, carrying value	$ 0.7	0.8
Held-to-maturity investments, fair value		$ 0.9
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate under Revolving Credit Facility	1.375%
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate under Revolving Credit Facility	2.00%