Equity-based Incentive Plans (Long-Term Incentive Compensation Program) (Details) - Senior Executive Officers	12 Months Ended
	Dec. 31, 2017 shares
Performance Shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards earned as percentage of specified compensation	0.00%
Performance Shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards earned as percentage of specified compensation	100.00%
2013 Award | Two-year performance period transition award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	173,319
Award Earned	159,457
2013 Award | Two-year performance period transition award | Performance/Service period one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	53,154
2013 Award | Two-year performance period transition award | Performance/Service period two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	66,252
2013 Award | Two-year performance period transition award | Performance/Service period three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	40,051
2013 Award | Three-year performance period award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	173,319
Award Earned	149,060
2013 Award | Three-year performance period award | Performance/Service period one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	74,179
2013 Award | Three-year performance period award | Performance/Service period two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	37,441
2013 Award | Three-year performance period award | Performance/Service period three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	37,440
2014 Award | Three-year performance period award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	204,741
Award Earned	204,741
2014 Award | Three-year performance period award | Performance/Service period one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	68,249
2014 Award | Three-year performance period award | Performance/Service period two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	68,247
2014 Award | Three-year performance period award | Performance/Service period three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	68,245
2015 Award | Three-year performance period award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	236,434
Award Earned	236,434
2015 Award | Three-year performance period award | Performance/Service period one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	78,813
2015 Award | Three-year performance period award | Performance/Service period two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	78,812
2015 Award | Three-year performance period award | Performance/Service period three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	78,809
2016 Award | Three-year performance period award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	324,469
2017 Award | One-year performance period transition award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	28,379
Award Earned	25,541
2017 Award | One-year performance period transition award | Performance/Service period one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	8,514
2017 Award | One-year performance period transition award | Performance/Service period two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	8,514
2017 Award | One-year performance period transition award | Performance/Service period three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Issued/Issuable	8,513
2017 Award | Two-year performance period transition award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	16,779
2017 Award | Three-year performance period award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Shares That Could Be Issued	182,274