Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash flows from operating activities
Net income	$ 28,859	$ 22,213
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	61,208	44,651
Stock-based compensation	7,493	4,849
Excess tax benefit from stock-based compensation	(5,796)	(4,118)
Imputed interest on deferred payment obligations	94	584
Gain on sale of patent assets	(177)	0
Amortization of premium on investments	3,773	404
Deferred taxes	(1,534)	99
Other	(19)	1
Changes in assets and liabilities:
Accounts receivable	3,163	10,586
Prepaid expenses and other assets	5,874	(4,777)
Deposit	(10,000)	0
Accounts payable	225	256
Accrued and other liabilities	(2,856)	7,543
Deferred revenue	(9,642)	14,974
Net cash provided by operating activities	80,665	97,265
Cash flows from investing activities
Purchases of investments classified as available-for-sale	(150,227)	(142,825)
Maturities and sale of investments classified as available-for-sale	153,920	15,100
Business acquisition	(45,765)	(3,345)
Decrease in restricted cash	647	73
Purchases of intangible assets	(52)	(95)
Purchases of property and equipment	(1,626)	(913)
Acquisitions of patent assets	(65,056)	(63,815)
Proceeds from sale of patent assets	200	80
Net cash used in investing activities	(107,959)	(195,740)
Cash flows from financing activities
Repayments of principal on deferred payment obligations	(5,150)	(18,104)
Proceeds from other obligations	500	0
Proceeds from issuance of common stock in initial public offering, net of issuance costs	0	157,478
Proceeds from issuance of common stock in follow-on offering, net of issuance costs	0	27,379
Proceeds from exercise of stock options and other common stock issuances	2,839	2,632
Excess tax benefit from stock-based compensation	5,796	4,118
Net cash provided by financing activities	3,985	173,503
Net increase (decrease) in cash and cash equivalents	(23,309)	75,028
Cash and cash equivalents at beginning of period	106,749	46,656
Cash and cash equivalents at end of period	83,440	121,684
Non-cash investing and financing activities
Conversion of redeemable convertible preferred stock to common stock	0	62,793
Change in patent assets purchased and accrued but not paid	250	6,626
Change in other assets purchased and accrued but not paid	565	0
Intangible assets received in barter transactions	54	120
Cost related to public offerings accrued but not paid	$ 0	$ 497