Note 2 - Stock-based Compensation - RSU Summary (Details)	6 Months Ended
	Jun. 30, 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	714,000
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 64.02
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 43.63
Released (in shares) | shares	(543,000)
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 39.96
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 57.05
Forfeited (in shares) | shares	(16,000)
Ending balance (in shares) | shares	4,425,000
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	69,000
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 91.57
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 46.84
Released (in shares) | shares	(103,000)
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 61.12
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 61.12
Forfeited (in shares) | shares	(10,000)
Ending balance (in shares) | shares	322,000
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	645,000	[1]
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 61.08
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 42.87
Released (in shares) | shares	(440,000)
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 47.92
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	$ 49.82
Forfeited (in shares) | shares	(6,000)
Ending balance (in shares) | shares	2,483,000
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
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares	23.57
Weighted-Average Grant Date Fair Value Per Share (in dollars per share) | $ / shares
Forfeited (in shares) | shares
Ending balance (in shares) | shares	1,620,000

[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.