Fair Value Measurements and Derivative Instruments (Narrative) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Investment securities at a loss position for more than 12 months, aggregate unrealized holding losses (less than at December 31, 2016)	$ 1,000,000	$ 1,000,000
Investment securities at a loss position for more than 12 months, estimated fair value	90,000,000	12,000,000
Investment securities at a loss position for less than 12 months, aggregate unrealized holding losses	1,000,000	4,000,000
Investment securities at a loss position for less than 12 months, estimated fair value	76,000,000	171,000,000
Amount of ineffectiveness	0
Term Loan | Notes due December 2020
Derivative [Line Items]
Loan amount	300,000,000
Foreign exchange contracts
Derivative [Line Items]
Derivative notional amount	12,000,000	$ 13,000,000
Interest rate swaps | Cash Flow Hedge
Derivative [Line Items]
Derivative notional amount	$ 300,000,000
Fixed interest rate	0.8826%