Acquisitions Cash Paid for Acquisitions (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Paid for Business Acquisitions [Line Items]
Cash paid for acquisitions completed during the year	$ 70,948	$ 17,284	$ 74,465
Cash paid for holdback payments during the current year	3,060	828	11,951
Earnout and other payments during the year	3,610	50	1,205
Total cash paid for acquisitions	$ 77,618	$ 18,162	$ 87,621