Summary of Significant Accounting Policies Accounts Receivable (Details) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bad Debt Expense	$ 1.8	$ 0.5	$ 2.1
Allowance for Doubtful Accounts Receivable	$ 4.8	$ 3.9