Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015 USD ($) Office subsidiary	Sep. 30, 2014
Accounting Policies [Abstract]
Number of domestic field offices of parent company | Office			63
Number of subsidiaries with international offices | subsidiary			1
Percentage of net service revenue from international operations (less than)	2.00%	2.00%	2.00%	2.00%
Health insurance maximum risk of loss liability per employee insurance plan			$ 300
Health insurance maximum aggregate amount of risk of loss liability for employee insurance plans			$ 450