Fair Value Measurements (Schedule of Non-Recurring Losses Recognized Using Fair Value Measurements and the Carrying Value of any Assets and Liabilities Measured Using Fair Value Estimates) (Details) - Nonrecurring - Net Assets of Acquired Businesses - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Assets, carrying value	$ 37,581	$ 41,808	$ 28,727
Assets, non-recurring losses	$ 0	$ 0	$ 0