Note 15 - Stock-based Compensation - Performance Stock Units Granted (Details) - Performance Shares [Member] $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) $ / shares shares
Maximum potential expense to be recognized | $	$ 14,915	[1]
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
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
Maximum potential expense to be recognized | $	$ 7,142	[1]
Chief Executive Officer [Member] | May 23, 2018 [Member]
Threshold goal, number of PSUs (in shares)	60,000
Target goal, number of PSUs (in shares)	120,000
Maximum goal, number of PSUs (in shares)	240,000
Maximum potential expense to be recognized | $	$ 6,629	[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
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
Fair value per share (in dollars per share) | $ / shares	$ 21.23
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
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
Fair value per share (in dollars per share) | $ / shares	$ 30.06
Chief Operating Officer [Member] | May 23, 2018 [Member]
Threshold goal, number of PSUs (in shares)	60,000
Target goal, number of PSUs (in shares)	120,000
Maximum goal, number of PSUs (in shares)	240,000
Maximum potential expense to be recognized | $	$ 6,629	[1]
Base period revenues | $	2,543,000
Threshold goal, home sale revenues | $	2,670,000
Target goal, home sale revenues | $	2,797,000
Maximum goal, home sale revenues | $	$ 3,052,000
Fair value per share (in dollars per share) | $ / shares	$ 27.62
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
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
Maximum potential expense to be recognized | $	$ 1,786	[1]
Chief Financial Officer [Member] | May 23, 2018 [Member]
Threshold goal, number of PSUs (in shares)	15,000
Target goal, number of PSUs (in shares)	30,000
Maximum goal, number of PSUs (in shares)	60,000
Maximum potential expense to be recognized | $	$ 1,657	[1]

[1] Dollars in thousands