Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income	$ 16,755	$ 15,144
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	4,810	2,864
Amortization and change in contingent consideration	19,946	14,657
Stock-based compensation	14,674	10,012
Loss on disposal of fixed assets	519	14
Provision for doubtful accounts	220	(441)
Deferred taxes	10,577	8,267
Excess tax benefit from the exercise of stock options	(5,260)	(7,706)
Changes in operating assets and liabilities:
Accounts receivable	(7,852)	(10,907)
Prepaid expenses and other current assets	(512)	(5,256)
Other assets	2,225	(2,608)
Accounts payable and accrued expenses	6,953	480
Customer obligations	27,952	(514)
Other liabilities	(1,172)	(1,055)
Net cash provided by operating activities	89,835	22,951
Cash flows from investing activities:
Purchases of property and equipment	(24,200)	(11,628)
Cash consideration for business acquisitions, net of cash acquired	(9,445)	(44,314)
Change in restricted cash		(1)
Net cash used in investing activities	(33,645)	(55,943)
Cash flows from financing activities:
Proceeds from debt		49,663
Proceeds from exercise of common stock options	4,695	4,726
Proceeds from issuance of common stock (Employee Stock Purchase Plan)	1,793	1,776
Payment of contingent consideration	(3,247)	(4,485)
Excess tax benefit from the exercise of stock options	5,260	7,706
Net cash provided by financing activities	8,501	59,386
Net increase in cash and cash equivalents	64,691	26,394
Cash and cash equivalents at beginning of period	413,301	359,958
Cash and cash equivalents at end of period	477,992	386,352
Cash paid during the period for:
Interest	2,079	866
Taxes	822	696
Supplemental disclosure of non-cash investing activities:
Accrued capital expenditures	$ 371	$ 900