Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities
Net income	$ 39,341	$ 40,783	$ 38,957
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	123,138	108,629	83,137
Stock-based compensation	17,656	16,115	10,334
Excess tax benefit from stock-based compensation	(2,598)	(3,857)	(8,574)
Imputed interest on deferred payment obligations	0	0	94
(Gain) loss on sale of patent assets, net	(707)	126	(177)
Amortization of premium on investments	6,585	6,013	5,131
Deferred taxes	(14,216)	(3,302)	1,477
Other	(500)	116	12
Changes in assets and liabilities:
Accounts receivable	14,006	(13,333)	(8,984)
Other receivables	0	33,775	(33,775)
Prepaid expenses and other assets	3,565	(9,376)	8,667
Accounts payable	(97)	(236)	(253)
Accrued and other liabilities	6,930	3,648	(711)
Deferred revenue	(1,634)	33,372	(3,958)
Net cash provided by operating activities	191,469	212,473	91,377
Cash flows from investing activities
Purchases of investments classified as available-for-sale	(224,548)	(210,660)	(185,582)
Maturities of investments classified as available-for-sale	174,650	147,052	188,026
Sales of investments classified as available-for-sale	0	1,099	0
Business acquisitions	(2,286)	0	(45,765)
(Increase) decrease in restricted cash	143	(1,818)	647
Purchases of intangible assets	0	0	(64)
Purchases of property and equipment	(1,511)	(2,880)	(1,726)
Acquisitions of patent assets	(136,968)	(127,101)	(87,366)
Payment of Deposit for Acquisition of Intangible Asset	(25,000)	0	0
Proceeds from sale of patent assets	1,086	100	200
Net cash used in investing activities	(214,434)	(194,208)	(131,630)
Cash flows from financing activities
Repayments of principal on deferred payment obligations	0	0	(5,150)
Proceeds from other obligations	0	0	500
Proceeds from exercise of stock options and other common stock issuances	3,159	5,151	3,218
Taxes paid related to net share settlements of restricted stock units	(4,928)	(756)	0
Excess tax benefit from stock-based compensation	2,598	3,857	8,574
Net cash provided by financing activities	829	8,252	7,142
Net increase (decrease) in cash and cash equivalents	(22,136)	26,517	(33,111)
Cash and cash equivalents at beginning of period	100,155	73,638
Cash and cash equivalents at end of period	78,019	100,155	73,638
Supplemental disclosures of cash flow information
Cash paid for interest	0	0	94
Cash paid for income taxes	15,066	17,849	4,672
Non-cash investing and financing activities
Change in patent assets purchased and accrued but not paid	(500)	(600)	1,100
Change in fixed assets purchased and accrued but not yet paid	(166)	166	0
Change in other assets purchased and accrued but not paid	(63)	63	(250)
Patent assets and intangible assets received in barter transactions	0	0	54
Issuance of Common Stock Related to Business Acquisition	3,156	0	0
Cost related to public offerings accrued but not paid	$ 425	$ 0	$ 0