CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities:
Net income	$ 90,908	$ 105,931	$ 5,035
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	17,195	21,214	25,295
Bad debt expense	224	884	2,969
Unrealized net loss (gain) on foreign currency forward contracts	0	1,641	(1,682)
Non-cash restructuring costs and adjustments	0	(136)	199
Deferred taxes	(4,983)	9,666	(1,526)
Release of liabilities for unrecognized tax benefits	(394)	(899)	0
Share-based compensation expense	11,817	17,299	11,786
Excess tax benefits from share-based compensation arrangements	(1,244)	(1,096)	0
Reclassification of foreign currency translation adjustment from other comprehensive income	0	(280)	0
Changes in operating assets and liabilities:
Accounts receivable	(16,878)	5,003	(276)
Prepaid expenses and other current assets	(880)	4,446	(2,713)
Deposits and other assets	(4,059)	1,631	909
Accounts payable and accrued expenses	6,981	1,904	(1,701)
Accrued compensation and employee benefits	3,787	(8,387)	(26,875)
Accrued restructuring costs	(58)	(1,922)	2,379
Deferred revenue and advance payments	11,238	(4,176)	731
Other long-term liabilities	(3,065)	(3,024)	70
Net cash provided by operating activities	110,589	149,699	14,600
Investing activities:
Proceeds from redemption of short-term investments	361,680	479,200	308,900
Purchases of property and equipment	(2,337)	(3,484)	(12,400)
Purchases of short-term investments	(354,999)	(473,779)	(370,050)
Capitalized software development costs	0	(9,598)	(8,396)
Increase in restricted cash	(135)	(20)	(164)
Net cash provided by (used in) investing activities	4,209	(7,681)	(82,110)
Financing activities:
Proceeds from sale of class A common stock under exercise of employee stock options	1,663	9,529	856
Payment of taxes relating to net exercise of employee stock options	(3,739)	0	0
Excess tax benefits from share-based compensation arrangements	1,244	1,096	0
Payments on capital lease obligations and other financing arrangements	(172)	(1,447)	(2,326)
Net cash (used in) provided by financing activities	(1,004)	9,178	(1,470)
Effect of foreign exchange rate changes on cash and cash equivalents	(4,160)	(5,774)	(4,272)
Net increase (decrease) in cash and cash equivalents	109,634	145,422	(73,252)
Cash and cash equivalents, beginning of year	292,341	146,919	220,171
Cash and cash equivalents, end of year	401,975	292,341	146,919
Supplemental disclosure of cash flow information:
Cash paid during the year for interest	2	34	74
Cash paid during the year for income taxes, net of tax refunds	24,332	13,346	5,529
Supplemental disclosure of noncash investing and financing activities:
Assets acquired under capital lease obligations and other financing arrangements	$ 0	$ 14	$ 70