Restatement - Cash Flows (Details) (USD $)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net income	$ 36,834,000	$ 28,621,000
Adjustments to reconcile net income to net cash used in operating activities:
Deferred income taxes	(2,251,000)	277,000
Unrealized loss on financial instruments	21,000	771,000
Loss recognized on disposition of fixed assets	(50,000)	1,010,000
Depreciation expense	14,830,000	13,568,000
Amortization of purchased intangible assets	7,041,000	6,920,000
Loss recognized on sale of available-for-sale marketable securities	0	28,000
Impairment of intangible asset	0	1,494,000
Stock-based compensation expense	16,094,000	14,990,000
Excess tax benefits from exercise and release of stock-based awards	(4,028,000)	(1,469,000)
Non-cash restructuring charges	0	146,000
Changes in operating assets and liabilities, excluding impact of acquisitions:
Accounts receivable	(18,724,000)	11,221,000
Unbilled revenues	(25,753,000)	(21,023,000)
Prepaid expenses and other current assets	(18,977,000)	(4,078,000)
Other assets	(521,000)	(179,000)
Accounts payable	1,508,000	5,162,000
Accrued compensation	(32,663,000)	(20,782,000)
Deferred revenues	(6,121,000)	(5,914,000)
Accrued expenses	15,511,000	1,133,000
Income taxes payable	(7,597,000)	4,353,000
Other long-term liabilities	8,075,000	4,134,000
Net cash (used in) provided by operating activities	(16,980,000)	40,383,000
Cash flows from investing activities:
Purchases of property and equipment and cost of internally developed software	(22,370,000)	(17,759,000)
Cash paid for acquisitions of businesses, net of cash acquired	(12,812,000)	(4,993,000)
Sales of marketable securities classified as available-for-sale	0	1,372,000
Purchases of marketable securities classified as available-for-sale	0	(251,000)
Acquisition of cost method investment	(5,526,000)	(200,000)
Cash paid on financial instruments, net	172,000	77,000
Change in restricted cash	373,000	3,515,000
Net cash used in investing activities	(41,624,000)	(18,239,000)
Cash flows from financing activities:
Excess tax benefits from exercise and release of stock-based awards	4,028,000	1,469,000
Proceeds from issuance of common stock under stock plans	2,288,000	1,960,000
Net cash (used in) provided by financing activities	(1,714,000)	3,429,000
Effect of exchange rate changes on cash and cash equivalents	3,825,000	(10,088,000)
Net (decrease) increase in cash and cash equivalents	(56,493,000)	15,485,000
Cash and cash equivalents at beginning of period	337,630,000	234,038,000
Cash and cash equivalents at end of period	281,137,000	249,523,000
As Reported [Member]
Cash flows from operating activities:
Net income		29,817,000
Adjustments to reconcile net income to net cash used in operating activities:
Deferred income taxes		1,233,000
Unrealized loss on financial instruments		771,000
Loss recognized on disposition of fixed assets		1,010,000
Depreciation expense		13,556,000
Amortization of purchased intangible assets		6,920,000
Loss recognized on sale of available-for-sale marketable securities		28,000
Impairment of intangible asset		1,494,000
Stock-based compensation expense		14,990,000
Excess tax benefits from exercise and release of stock-based awards		(1,469,000)
Non-cash restructuring charges		146,000
Changes in operating assets and liabilities, excluding impact of acquisitions:
Accounts receivable		11,221,000
Unbilled revenues		(21,023,000)
Prepaid expenses and other current assets		(4,078,000)
Other assets		(179,000)
Accounts payable		5,162,000
Accrued compensation		(19,139,000)
Deferred revenues		(5,914,000)
Accrued expenses		1,076,000
Income taxes payable		3,827,000
Other long-term liabilities		934,000
Net cash (used in) provided by operating activities		40,383,000
Cash flows from investing activities:
Purchases of property and equipment and cost of internally developed software		(17,759,000)
Cash paid for acquisitions of businesses, net of cash acquired		(4,993,000)
Sales of marketable securities classified as available-for-sale		1,372,000
Purchases of marketable securities classified as available-for-sale		(251,000)
Acquisition of cost method investment		(200,000)
Cash paid on financial instruments, net		77,000
Change in restricted cash		3,515,000
Net cash used in investing activities		(18,239,000)
Cash flows from financing activities:
Excess tax benefits from exercise and release of stock-based awards		1,469,000
Proceeds from issuance of common stock under stock plans		1,960,000
Net cash (used in) provided by financing activities		3,429,000
Effect of exchange rate changes on cash and cash equivalents		(10,088,000)
Net (decrease) increase in cash and cash equivalents		15,485,000
Cash and cash equivalents at beginning of period		234,038,000
Cash and cash equivalents at end of period		249,523,000
Adjustments [Member]
Cash flows from operating activities:
Net income		(1,196,000)
Adjustments to reconcile net income to net cash used in operating activities:
Deferred income taxes		(956,000)
Unrealized loss on financial instruments		0
Loss recognized on disposition of fixed assets		0
Depreciation expense		12,000
Amortization of purchased intangible assets		0
Loss recognized on sale of available-for-sale marketable securities		0
Impairment of intangible asset		0
Stock-based compensation expense		0
Excess tax benefits from exercise and release of stock-based awards		0
Non-cash restructuring charges		0
Changes in operating assets and liabilities, excluding impact of acquisitions:
Accounts receivable		0
Unbilled revenues		0
Prepaid expenses and other current assets		0
Other assets		0
Accounts payable		0
Accrued compensation		(1,643,000)
Deferred revenues		0
Accrued expenses		57,000
Income taxes payable		526,000
Other long-term liabilities		3,200,000
Net cash (used in) provided by operating activities		0
Cash flows from investing activities:
Purchases of property and equipment and cost of internally developed software		0
Cash paid for acquisitions of businesses, net of cash acquired		0
Sales of marketable securities classified as available-for-sale		0
Purchases of marketable securities classified as available-for-sale		0
Acquisition of cost method investment		0
Cash paid on financial instruments, net		0
Change in restricted cash		0
Net cash used in investing activities		0
Cash flows from financing activities:
Excess tax benefits from exercise and release of stock-based awards		0
Proceeds from issuance of common stock under stock plans		0
Net cash (used in) provided by financing activities		0
Effect of exchange rate changes on cash and cash equivalents		0
Net (decrease) increase in cash and cash equivalents		0
Cash and cash equivalents at beginning of period		0
Cash and cash equivalents at end of period		$ 0