Consolidated Statement of Changes in Shareholders' Equity (Parenthetical) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retained Earnings [Member]
Common stock per share dividend amount	$ 3.00	$ 2.80	$ 2.80
Series A Warrants [Member] | Common Stock [Member]
Exercise of warrants into shares of common stock			2,315
Exercise of warrants into shares of common stock			904
Series A Warrants [Member] | Treasury Stock [Member]
Exercise of warrants into shares of common stock	374,786	87,381
Exercise of warrants into shares of common stock	204,133	41,439