Note 15 - Stock-based Compensation - Performance Stock Units Granted (Details) - Performance Shares [Member] $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) $ / shares shares
July 25, 2016 [Member]
Maximum potential expense to be recognized | $	$ 10,834	[1]
June 20, 2017 [Member]
Maximum potential expense to be recognized | $	$ 16,070	[1]
Chief Executive Officer [Member] | July 25, 2016 [Member]
Threshold goal, number of PSUs (in shares)	56,700
Target goal, number of PSUs (in shares)	113,400
Maximum goal, number of PSUs (in shares)	226,800
Fair value per share (in dollars per share) | $ / shares	$ 22.93
Maximum potential expense to be recognized | $	$ 4,815	[1]
Chief Executive Officer [Member] | June 20, 2017 [Member]
Threshold goal, number of PSUs (in shares)	59,400
Target goal, number of PSUs (in shares)	118,800
Maximum goal, number of PSUs (in shares)	237,600
Fair value per share (in dollars per share) | $ / shares	$ 30.92
Maximum potential expense to be recognized | $	$ 7,142	[1]
Chief Operating Officer [Member] | July 25, 2016 [Member]
Threshold goal, number of PSUs (in shares)	56,700
Target goal, number of PSUs (in shares)	113,400
Maximum goal, number of PSUs (in shares)	226,800
Fair value per share (in dollars per share) | $ / shares	$ 21.23
Maximum potential expense to be recognized | $	$ 4,815	[1]
Base period revenues | $	1,975,000
Threshold goal, home sale revenues | $	2,074,000
Target goal, home sale revenues | $	2,173,000
Maximum goal, home sale revenues | $	$ 2,370,000
Chief Operating Officer [Member] | June 20, 2017 [Member]
Threshold goal, number of PSUs (in shares)	59,400
Target goal, number of PSUs (in shares)	118,800
Maximum goal, number of PSUs (in shares)	237,600
Fair value per share (in dollars per share) | $ / shares	$ 30.06
Maximum potential expense to be recognized | $	$ 7,142	[1]
Base period revenues | $	2,426,000
Threshold goal, home sale revenues | $	2,547,000
Target goal, home sale revenues | $	2,669,000
Maximum goal, home sale revenues | $	$ 2,911,000
Chief Financial Officer [Member] | July 25, 2016 [Member]
Threshold goal, number of PSUs (in shares)	14,175
Target goal, number of PSUs (in shares)	28,350
Maximum goal, number of PSUs (in shares)	56,700
Fair value per share (in dollars per share) | $ / shares	$ 22.93
Maximum potential expense to be recognized | $	$ 1,204	[1]
Chief Financial Officer [Member] | June 20, 2017 [Member]
Threshold goal, number of PSUs (in shares)	14,850
Target goal, number of PSUs (in shares)	29,700
Maximum goal, number of PSUs (in shares)	59,400
Fair value per share (in dollars per share) | $ / shares	$ 30.92
Maximum potential expense to be recognized | $	$ 1,786	[1]

[1] Dollars in thousands