Stockholders' Equity Earnings Per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Weighted average number of shares outstanding - basic	51,182,502	52,590,837	51,436,228	52,463,511
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	1,521,560	1,863,883	1,525,204	1,789,307
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	1,559,830	1,329,765	1,559,830	1,329,765
Weighted Average Number of Shares Outstanding, Diluted	54,263,892	55,784,485	54,521,262	55,582,583