Acquisitions (Cash Paid for Acquisitions) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Combinations [Abstract]
Cash paid for acquisitions completed during the year	$ 0	$ 196,395	$ 70,948
Cash paid for holdback payments during the year	1,014	3,404	3,060
Earn-out and other payments during the year	5,617	1,453	3,610
Total cash paid for acquisitions	$ 6,631	$ 201,252	$ 77,618