Note 9 - Stock-based Compensation (Details) - Share-based Compensation Activity (USD $)	6 Months Ended	12 Months Ended				6 Months Ended	12 Months Ended		6 Months Ended	12 Months Ended				6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jun. 30, 2014 Restricted Stock [Member] Mercantile Plans [Member]	Dec. 31, 2013 Restricted Stock [Member] Mercantile Plans [Member]	Dec. 31, 2012 Restricted Stock [Member] Mercantile Plans [Member]	Jun. 30, 2014 Restricted Stock [Member]	Dec. 31, 2013 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member]	Dec. 31, 2010 Restricted Stock [Member]	Dec. 31, 2009 Restricted Stock [Member]	Jun. 30, 2014 Mercantile Plans [Member]	Dec. 31, 2013 Mercantile Plans [Member]	Dec. 31, 2012 Mercantile Plans [Member]
Note 9 - Stock-based Compensation (Details) - Share-based Compensation Activity [Line Items]
Nonvested, shares						63,800	66,100	38,650
Nonvested, weighted average fair value						$ 14.30	$ 14.30	$ 6.20
Outstanding, shares														60,876	152,896	214,903
Outstanding, weighted average exercise price														$ 33.11	$ 26.15	$ 22.40
Options exercisable at period-end														56,890	60,876	152,896
Options exercisable at period-end														$ 33.79	$ 33.11	$ 26.15
Granted	0	0	0	0	0									0	0	0
Granted
Exercised														(2,845)	(51,055)	(50,930)
Exercised														$ 17.74	$ 13.72	$ 10.83
Forfeited or expired														(1,141)	(40,965)	(11,077)
Forfeited or expired														$ 37.55	$ 31.30	$ 23.77
Granted						0	0	66,100	0	0	0	0	0
Granted								$ 14.30
Vested						(63,300)	0	(38,266)
Vested						$ 14.30		$ 6.20
Forfeited						(500)	(2,300)	(384)
Forfeited						$ 14.30	$ 14.30	$ 6.20
Nonvested, shares						0	63,800	66,100
Nonvested, weighted average fair value							$ 14.30	$ 14.30
Outstanding, shares														56,890	60,876	152,896
Outstanding, weighted average exercise price														$ 33.79	$ 33.11	$ 26.15