Note 2 - Summary of Significant Accounting Policies - Components Used in Computation of Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								11 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 13, 2014	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Net income	$ 166,961	$ 132,348	$ 112,760	$ 72,661	$ 77,529	$ 47,177	$ 57,198	$ 31,605	$ 215,865	$ 484,730	[1]	$ 213,509	[1]	$ 215,865
Less: Net income allocated to preferred shareholder									(51,650)			(32,997)		(51,650)
Less: Net income allocated to unvested restricted stock									(297)	(1,168)		(369)		(297)
Net income available to common stockholders for basic earnings per common share									163,918	483,562		180,143		163,918
Effect of dilutive securities:
Net income allocated to preferred shareholder									$ 51,650			32,997		51,650
Net income available to common and preferred stock for diluted earnings per share										$ 488,890		$ 214,094		$ 216,467
Basic (in shares)									55,737,548	118,212,740		71,713,747		55,737,548
Weighted average additional common shares outstanding if preferred shares converted to common shares (if dilutive) (in shares)												13,135,814		17,562,557
Total weighted average common shares outstanding if preferred shares converted to common shares (in shares)										118,212,740		84,849,561		73,300,105
Share-based awards (in shares)										666,928		816,459		1,256,964
Weighted average diluted shares outstanding (in shares)									80,819,639	135,984,985		94,648,767		80,819,639
Income per common share:
Basic income per common share (in dollars per share)	$ 1.44	$ 1.12	$ 0.95	$ 0.60	$ 0.64	$ 0.65	$ 0.80	$ 0.45	$ 2.94	$ 4.09	[1]	$ 2.51	[1]	$ 2.94
Diluted income per common share (in dollars per share)	$ 1.25	$ 0.97	$ 0.83	$ 0.52	$ 0.56	$ 0.59	$ 0.70	$ 0.40	$ 2.68	$ 3.60	[1]	$ 2.26	[1]	$ 2.68
1.625% Convertible Senior Notes due May 2018 [Member]
Effect of dilutive securities:
Interest on convertible senior notes										$ 2,059		$ 47
Interest on convertible senior notes (in shares)										7,167,960		1,804,192
0.25% Convertible Senior Notes Due June 2019 [Member]
Effect of dilutive securities:
Interest on convertible senior notes										$ 1,862		$ 9
Interest on convertible senior notes (in shares)										3,639,150		915,985
1.25% Convertible Senior Notes Due August 2032 [Member]
Effect of dilutive securities:
Interest on convertible senior notes										$ 1,407		$ 898		$ 899
Interest on convertible senior notes (in shares)										6,298,207		6,262,570		6,262,570

[1] Per share amounts do not add across due to rounding differences in quarterly amounts and due to the impact of differences between the quarterly and annual weighted average share calculations.