Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net income	$ 11,031	$ 8,628
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	1,621	1,831
Amortization and change in contingent consideration	8,969	9,187
Stock-based compensation	6,278	3,558
Loss on disposal of fixed assets	14	82
Provision for doubtful accounts	(342)	(15)
Deferred taxes	6,288	4,372
Excess tax benefit from the exercise of stock options	(6,428)	(4,908)
Changes in operating assets and liabilities:
Accounts receivable	(5,767)	(8,868)
Prepaid expenses and other current assets	(723)	(2,185)
Other assets	(2,318)	215
Accounts payable and accrued expenses	(7,292)	1,594
Customer obligations	(967)	18,212
Other liabilities	(640)	(2,045)
Net cash provided by operating activities	9,724	29,658
Cash flows from investing activities:
Purchases of property and equipment	(7,067)	(7,421)
Cash consideration for business acquisitions, net of cash acquired		(751)
Cash paid for acquisition of client contracts		(1,219)
Change in restricted cash	(1)	3,248
Net cash used in investing activities	(7,068)	(6,143)
Cash flows from financing activities:
Proceeds from follow-on offering net of underwriters commissions and discounts		11,550
Proceeds from exercise of common stock options	3,797	8,825
Proceeds from issuance of common stock (Employee Stock Purchase Plan)	1,363	1,132
Payment of contingent consideration	(3,308)
Excess tax benefit from the exercise of stock options	6,428	4,908
Net cash provided by financing activities	8,280	26,415
Net increase in cash and cash equivalents	10,936	49,930
Cash and cash equivalents at beginning of period	359,958	305,052
Cash and cash equivalents at end of period	370,894	354,982
Cash paid during the period for:
Interest	444	911
Taxes	$ 82	$ 486