Goodwill and Other Intangibles (Changes in Net Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, beginning balance	$ 785,399	$ 757,142
Change in goodwill	3,659	28,257
Goodwill, ending balance	$ 789,058	$ 785,399