Stock-based Compensation (Summary Of RSU Vested And Expected To Vest) (Details) - RSUs [Member] - shares	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSU granted	70,688
Number of RSUs oustanding	222,939	274,134
Equity Incentive Plan 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSU granted	385,159
Number of RSUs oustanding	222,939
RSU vested and expected to vest	222,939
Equity Incentive Plan 2014 [Member] | December 31, 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	88,203
Equity Incentive Plan 2014 [Member] | December 31, 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	91,582
Equity Incentive Plan 2014 [Member] | December 31, 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	18,707
Equity Incentive Plan 2014 [Member] | December 31, 2021[Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	24,447
Equity Incentive Plan 2014 [Member] | Twenty Fifteen [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSU granted	112,868
Number of RSUs oustanding	5,481
RSU vested and expected to vest	5,481
Equity Incentive Plan 2014 [Member] | Twenty Fifteen [Member] | December 31, 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	5,481
Equity Incentive Plan 2014 [Member] | Twenty Sixteen [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSU granted	107,274
Number of RSUs oustanding	75,911
RSU vested and expected to vest	75,911
Equity Incentive Plan 2014 [Member] | Twenty Sixteen [Member] | December 31, 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	68,365
Equity Incentive Plan 2014 [Member] | Twenty Sixteen [Member] | December 31, 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	7,546
Equity Incentive Plan 2014 [Member] | Twenty Seventeen [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSU granted	94,329
Number of RSUs oustanding	76,033
RSU vested and expected to vest	76,033
Equity Incentive Plan 2014 [Member] | Twenty Seventeen [Member] | December 31, 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	62,857
Equity Incentive Plan 2014 [Member] | Twenty Seventeen [Member] | December 31, 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	9,926
Equity Incentive Plan 2014 [Member] | Twenty Seventeen [Member] | December 31, 2021[Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	3,250
Equity Incentive Plan 2014 [Member] | Twenty Eighteen [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSU granted	70,688
Number of RSUs oustanding	65,514
RSU vested and expected to vest	65,514
Equity Incentive Plan 2014 [Member] | Twenty Eighteen [Member] | December 31, 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	14,357
Equity Incentive Plan 2014 [Member] | Twenty Eighteen [Member] | December 31, 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	21,179
Equity Incentive Plan 2014 [Member] | Twenty Eighteen [Member] | December 31, 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	8,781
Equity Incentive Plan 2014 [Member] | Twenty Eighteen [Member] | December 31, 2021[Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vested and expected to vest	21,197