Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities:
Net income	$ 14,331	$ 28,486
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of property and equipment	20,599	18,875
Amortization of intangible assets	15,947	15,101
Amortization of deferred financing costs	1,563	1,563
Stock-based compensation expense	16,761	10,747
Deferred income taxes	(726)	(5,902)
(Gain) / Loss on disposal of assets		(970)
Change in fair value of contingent consideration	2,450
Changes in operating assets and liabilities, net of acquisition:
Accounts receivable	5,630	8,534
Prepaid expenses	757	(1,905)
Other current assets	712	2,579
Other assets	163	(38)
Income taxes receivable / (payable)	(2,731)	(15,368)
Accounts payable, accrued expenses and other liabilities	(20,357)	(2,584)
Estimated liability for appeals	(1)	(2,896)
Net cash provided by operating activities	55,098	56,222
Investing activities:
Acquisition of a business, net of cash acquired	(171,174)	(20,910)
Proceeds from sale of cost basis investment		2,496
Purchases of property and equipment	(11,656)	(8,796)
Investment in capitalized software	(10,664)	(4,910)
Net cash used in investing activities	(193,494)	(32,120)
Financing activities:
Proceeds from exercise of stock options	2,580	2,940
Payments of tax withholdings on behalf of employees for net-share settlement for stock-based compensation	(2,898)	(1,090)
Payments on capital lease obligations	(5)	(43)
Proceeds from revolving credit facility	42,204
Net cash provided by financing activities	41,881	1,807
Net (decrease) / increase in cash and cash equivalents	(96,515)	25,909
us-gaap_CashAndCashEquivalentsAbstract
Cash and cash equivalents at beginning of year	175,999	145,610
Cash and cash equivalents at end of period	79,484	171,519
Supplemental disclosure of cash flow information:
Cash paid for income taxes	12,317	19,478
Cash paid for interest	5,819	4,597
Supplemental disclosure of non-cash activities:
Change in balance of accrued property and equipment purchases	$ (414)	$ (176)