Consolidated Statements of Changes in Stockholders' Equity (Parentheticals) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock [Member]
Stock issued to directors, shares (in shares)	162,000	187,000	189,000
Common stock issued for cash, shares (in shares)	2,565,000	1,829,000	2,780,000
Stock issued for 401(k) match, shares (in shares)	1,068,000	678,000	1,128,000
Restricted stock unit distributions, shares (in shares)	1,079,000	1,251,000	1,390,000
Common stock issued to pension plans, shares (in shares)	2,736,000		1,827,000
Common stock issued for purchase of another company, shares (in shares)	75,276,000		8,852,000
Common stock dividends declared, per common share (in dollars per share)	$ 0.01	$ 0.01
Common stock issued for employee incentive compensation, shares (in shares)	1,237,000	533,000	2,185,000
Retained Earnings [Member]
Common stock dividends declared, per common share (in dollars per share)			$ 0.01
Common stock issued for cash, shares (in shares)	2,564,767