Note 6 - Summary of Activity for Metro Bonds (Details) - Metropolitan District Bond Securities [Member] - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Balance at beginning of period	$ 25,911	$ 18,203
Increase in fair value (recorded in other comprehensive income)	950	1,418
Change due to accretion of principal	$ 416	$ 357
Cash receipts
Balance at end of period	$ 27,277	$ 19,978

The fair value as of the balance sheet date of firm holdings in fixed income obligations issued by state and local governments and authorities. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 320
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant