Consolidated Statement of Changes in Shareholders' Equity (Unaudited) (Parenthetical) - $ / shares shares in Thousands	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017
Common stock per share dividend amount	$ 1.55	$ 1.50
Retained Earnings [Member]
Common stock per share dividend amount	$ 1.55	$ 1.50
Series A Warrants [Member] \| Treasury Stock [Member]
Exercise of warrants into shares of common stock	54,226	146,157
Exercise of warrants into shares of common stock	32,668	79,470

Number of shares issued during the period as a result of the conversion of convertible securities.

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