Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2018

Stockholders' Equity Note [Abstract]

Schedule of Weighted Average Number of Shares [Table Text Block]

The following table provides the computation of diluted weighted average number of common shares outstanding:

	Year Ended December 31,
	2018	2017	2016
Computation of diluted weighted average shares outstanding:
Basic weighted average shares outstanding	51,487,557	52,523,272	52,276,951
Incremental shares from assumed exercise of stock options and vesting of restricted stock	1,499,713	1,793,375	1,705,224
Incremental shares from assumed conversion of convertible debentures	1,640,477	799,680	18,904
Diluted weighted average shares outstanding	54,627,747	55,116,327	54,001,079