CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from operating activities:
Net income	$ 39,895	$ 38,187
Adjustments to reconcile net income to net cash provided by operating activities:
Stock based compensation expense	3,694	822
Depreciation	8,924	7,003
Amortization of intangibles	803	2,966
Amortization/accretion of premiums or discounts on short-term investments	455
Deferred income taxes	(2,795)	1,378
Loss on disposal of long-lived assets	4
Loss on impairment of longlived assets		131
Changes in assets and liabilities:
Accounts receivable	(43,021)	(25,358)
Prepaid expenses and other current assets	(1,499)	(1,335)
Income taxes receivable	6,797	4,772
Other assets	308	(831)
Accounts payable	(139)	738
Accrued compensation	(712)	3,173
Other liabilities	19	148
Deferred rent	(241)	(35)
Deferred revenue	(1,471)	(129)
Income taxes payable	8,715	615
Net cash provided by operating activities	19,736	32,245
Cash flows from investing activities:
Purchases of short-term investments	(611,095)
Maturities and sales of short-term investments	6,429
Purchases of property and equipment	(2,391)	(3,312)
Investment in capitalized software	(10,282)	(7,541)
Proceeds from sale of property and equipment		22
Net cash used in investing activities	(617,339)	(10,831)
Cash flows from financing activities:
Proceeds from issuance of common stock, net of underwriters' discount	362,082
Proceeds from issuance of treasury stock, net of underwriters' discount	282,172
Payment of offering costs	(5,182)
Repayment of credit facility borrowings	(10,000)
Repurchase of common stock		(9,066)
Dividends paid		(2,852)
Capital lease obligations paid	(53)	(67)
Excess tax benefits from stock based compensation	223
Proceeds from exercise of stock options	227	57
Net cash provided by (used in) financing activities	629,469	(11,928)
Increase in cash and cash equivalents	31,866	9,486
Cash and cash equivalents, beginning of period	162,567	110,594
Cash and cash equivalents, end of period	194,433	120,080
Supplementary cash flow disclosure:
Cash paid during the period for: Income taxes, net of refunds	16,924	17,756
Cash paid during the period for: Interest	2,189
Noncash investing activities:
Capital lease obligations incurred	175	14
Accounts payable for purchases of and investment in property, equipment and capitalized software	1,576	2,320
Accrued compensation for investment in capitalized software	$ 297	$ 616