Changes in the Carrying Value of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill Roll Forward
Net carrying value at beginning of period	$ 129,706	$ 129,706	$ 106,100
Acquisitions	10,932	0	23,606
Net carrying value at end of period	$ 140,638	$ 129,706	$ 129,706