Summary of Significant Accounting Policies Provision for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Doubtful Accounts Receivable, Period Increase (Decrease)	$ 3,992	$ 1,705	$ 2,364
Provision for Loan and Lease Losses	$ 1,129	$ 2,271	$ 714