Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities
Net income	$ 25,392	$ 21,269
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	47,798	38,938
Stock-based compensation	8,186	5,012
Excess tax benefit from stock-based compensation	(2,009)	(5,423)
Imputed interest on deferred payment obligations	0	93
(Gain) loss on sale of patent assets	126	(177)
Amortization of premium on investments	2,995	2,473
Deferred taxes	(1,906)	588
Other	13	(11)
Changes in assets and liabilities:
Accounts receivable	216	2,617
Other receivables	33,775	0
Prepaid expenses and other assets	(3,348)	3,745
Accounts payable	130	(226)
Accrued and other liabilities	(1,191)	(3,987)
Deferred revenue	13,202	(2,349)
Net cash provided by operating activities	123,379	62,562
Cash flows from investing activities
Purchases of investments classified as available-for-sale	(98,950)	(127,932)
Maturities of investments classified as available-for-sale	65,787	105,887
Sales of investments classified available-for-sale securities	1,099	0
Business acquisition	0	(45,765)
Decrease in restricted cash	0	647
Purchases of intangible assets	0	(52)
Purchases of property and equipment	(874)	(1,400)
Acquisitions of patent assets	(69,637)	(36,730)
Proceeds from sale of patent assets	100	200
Net cash used in investing activities	(102,475)	(105,145)
Cash flows from financing activities
Repayments of principal on deferred payment obligations	0	(4,050)
Proceeds from exercise of stock options and other common stock issuances	2,727	2,520
Excess tax benefit from stock-based compensation	2,009	5,423
Net cash provided by financing activities	4,736	3,893
Net increase (decrease) in cash and cash equivalents	25,640	(38,690)
Cash and cash equivalents at beginning of period	73,638	106,749
Cash and cash equivalents at end of period	99,278	68,059
Non-cash investing and financing activities
Change in patent assets purchased and accrued but not paid	1,100	2,200
Change in other assets purchased and accrued but not paid	550	2,430
Intangible assets received in barter transactions	$ 0	$ 54