Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities
Net income	$ 8,024	$ 6,937	$ 16,121
Adjustments to reconcile net income including non-controlling interests to net cash provided by operating activities:
Depreciation and amortization of property and equipment	15,958	12,301	7,511
Amortization of intangible assets	1,103	1,655	2,491
Stock-based compensation expense	2,735	3,450	867
Forgiveness on note receivable from stockholder		103
Excess tax benefits from stock-based compensation	1,818
Change in fair value of preferred stock warrants		132	68
Change in deferred taxes	989	2,828	(10,401)
Changes in operating assets and liabilities, net of effect of acquisition:
Accounts receivable	(3,011)	564	(2,006)
Prepaid expenses and other assets	(347)	527	(1,034)
Accounts payable	(290)	(1,236)	1,686
Accrued expenses and other liabilities	(2,506)	(83)	(382)
Deferred revenue	123	2,351	9,239
Net cash provided by operating activities	24,596	29,529	24,160
Cash flows from investing activities
Decrease in restricted cash	435	536	966
Purchases of marketable securities	(70,185)		(9,373)
Proceeds from sales of marketable securities	28,627	9,373
Purchases of property and equipment	(18,000)	(16,917)	(11,256)
Payments for patents, trademarks and domain	(146)	(156)
Payments for business acquisition, net of cash acquired	(3,185)
Contractual payments related to business acquisition	(14)	(171)	(271)
Net cash used in investing activities	(62,468)	(7,335)	(19,934)
Cash flows from financing activities
Proceeds from issuance of common stock upon initial public offering		48,297
Offering costs		(2,586)
Proceeds from exercise of stock options	2,573	1,028	2
Excess tax benefits from stock-based compensation	372	246
Payments of capital leases	(190)	(420)	(738)
Payments to non-controlling interests	(678)	(547)	(398)
Net cash provided by (used in) financing activities	2,077	46,018	(1,134)
Net (decrease) increase in cash and cash equivalents	(35,795)	68,212	3,092
Cash and cash equivalents at beginning of year	93,933	25,721	22,629
Cash and cash equivalents at end of year	58,138	93,933	25,721
Supplemental disclosure of cash flow information
Cash paid for interest	11	11	30
Cash paid for taxes	737	1,357	1,030
Supplemental disclosure of non-cash investing and financing activities
Conversion of convertible preferred stock into common stock		124,602
Retirement of treasury stock		4,575
Property and equipment and software maintenance costs in accounts payable, accrued expenses and other liabilities	2,607	1,995	3,319
Accretion of convertible preferred stock		1,633	5,020
Exercise and conversion of preferred stock warrants into common stock		272
Acquisition of software, equipment and software maintenance services under capital leases		402	73
Offering costs related to stock options issued to non-employee consultant		27
Contractual payments related to business acquisition in accrued expenses and other liabilities		14	47
Offering costs in accounts payable, accrued expenses and other liabilities		$ 10

Name:	us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.