Note 2 - Stock-based Compensation - RSU Summary (Details)	3 Months Ended
	Mar. 31, 2017 $ / shares shares
Beginning balance (in shares) | shares	4,270,000
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 36.47
Granted (in shares) | shares	574,000
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 65.02
Released (in shares) | shares	(421,000)
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 44.16
Forfeited (in shares) | shares	(8,000)
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 57.51
Ending balance (in shares) | shares	4,415,000
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 39.41
Time-Based RSUs [Member]
Beginning balance (in shares) | shares	366,000
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 51.35
Granted (in shares) | shares	47,000
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 89.37
Released (in shares) | shares	(61,000)
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 46.83
Forfeited (in shares) | shares	(5,000)
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 60.85
Ending balance (in shares) | shares	347,000
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 57.12
PSUs and MPSUs [Member]
Beginning balance (in shares) | shares	2,284,000
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 43.24
Granted (in shares) | shares	527,000	[1]
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 62.86
Released (in shares) | shares	(360,000)
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 43.71
Forfeited (in shares) | shares	(3,000)
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 52.30
Ending balance (in shares) | shares	2,448,000
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 47.38
MSUs [Member]
Beginning balance (in shares) | shares	1,620,000
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 23.57
Forfeited (in shares) | shares
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares
Ending balance (in shares) | shares	1,620,000
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 23.57

[1] Amount reflects the number of PSUs and MPSUs that may ultimately be earned based on management's probability assessment of the performance conditions at each reporting period. In addition, MPSUs are subject to the achievement of market conditions.