Consolidated Statements of Changes in Stockholders' Equity (Parentheticals) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common Stock [Member] | Stock Issued to Directors [Member]
Stock issued to directors, shares (in shares)	187,000	189,000	235,000
Common Stock [Member] | Stock Issued for 401(K) Match [Member]
Stock issued for 401(k) match, shares (in shares)	678,000	1,128,000	1,331,000
Common Stock [Member]
Stock issued to directors, shares (in shares)	533,000	2,185,000	871,000
Stock issued for 401(k) match, shares (in shares)		1,827,000	1,764,000
Restricted stock unit distributions, shares (in shares)	1,251,000	1,390,000	896,000
Common stock issued for purchase of another company, shares (in shares)		8,852,000	6,253,000
Common stock issued for cash, shares (in shares)	1,829,000	2,780,000
Retained Earnings [Member]
Common stock dividends declared, per common share (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Treasury Stock [Member]
Repurchase of common shares, shares (in shares)			284,000
Common stock issued for cash, shares (in shares)	1,828,760