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, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques
Assets, carrying value	$ 128,725	$ 35,224	$ 41,808
Assets, non-recurring losses/(gains)	$ 0	$ 0	$ 0