Debt (Revolving Facility) (Narrative) (Details) - Line of Credit - Revolving Facility - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Jun. 19, 2015	Dec. 19, 2014
Line of Credit Facility [Line Items]
Revolving Credit, maximum borrowing capacity			$ 1,650.0
Revolving Facility, amount outstanding	$ 0.0	$ 0.0
Revolving Facility, interest rate	1.325%
Facility fee, percentage	0.175%
Letters of credit
Line of Credit Facility [Line Items]
Revolving Credit, maximum borrowing capacity				$ 150.0
Subfacility
Line of Credit Facility [Line Items]
Revolving Credit, maximum borrowing capacity				$ 125.0