CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Revenues
Royalties	$ 143,617	$ 125,904	$ 235,464	$ 203,248
Total revenues	143,617	125,904	235,464	203,248
Operating expenses
General and administrative	6,783	5,145	13,969	12,090
Operating income	136,834	120,759	221,495	191,158
Non-operating expense, net
Interest and other income, net	4,963	428	8,801	518
Interest expense	(6,051)	(7,872)	(12,051)	(16,573)
Total non-operating expense, net	(1,088)	(7,444)	(3,250)	(16,055)
Income before income taxes	135,746	113,315	218,245	175,103
Income tax expense	42,004	39,813	71,032	61,417
Net income	$ 93,742	$ 73,502	$ 147,213	$ 113,686
Net income per share
Basic (in Dollars per Share)	$ 0.67	$ 0.53	$ 1.05	$ 0.81
Diluted (in Dollars per Share)	$ 0.62	$ 0.52	$ 0.96	$ 0.80
Weighted average shares outstanding
Basic (in Shares)	139,825	139,683	139,821	139,681
Diluted (in Shares)	152,224	142,213	152,784	142,890
Cash dividends declared per common share (in Dollars per Share)	$ 0.00	$ 0.00	$ 0.60	$ 0.60