CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Common stock, par value beginning balance	$ 0.001	$ 0.001
Options exercised, shares	33,764	84,850
Conversion of common stock units, shares	15,981	8,538
Conversion of restricted stock units, shares	247,620	165,794
Cash dividends, per share	$ 0.275	$ 0.265
Treasury stock, beginning balance, shares	24,672,932	23,971,522
Treasury stock, acquisition of shares	0	474,277
Treasury stock, ending balance, shares	24,672,932	24,445,799