CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Issuance of shares of common stock for acquisition of PAY.ON			227,917
Repurchase of common stock, shares	1,653,573	3,020,926
PAY.ON RSAs [Member]
Issuance of shares under stock plan portion of PAY.ON acquisition agreement			476,750