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Consolidated Statement of Stockholder's Equity (Parenthetical) - $ / shares
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]      
Cash dividends, per share (in dollars per share) $ 0.4750 $ 0.3750 $ 0.2850