Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - shares	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Common stock withheld to satisfy income tax withholding obligations relating to restricted stock units (shares)	625,704	210,029

For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

No definition available.

Name:	us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration