Other Comprehensive Income (Reclassifications from AOCI) (Details) - USD ($)
$ in Thousands |
3 Months Ended |
9 Months Ended |
Sep. 30, 2017 |
Sep. 30, 2016 |
Sep. 30, 2017 |
Sep. 30, 2016 |
| Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |
|
|
|
|
|
| Total, pre-tax |
|
$ (105,050)
|
$ (103,210)
|
$ (199,908)
|
$ (189,024)
|
| Tax benefit |
|
37,269
|
34,864
|
71,710
|
65,944
|
| Total amounts reclassified, net of tax |
|
26
|
44
|
75
|
129
|
| Gains and Losses on Cash Flow Hedges |
|
|
|
|
|
| Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |
|
|
|
|
|
| Total amounts reclassified, net of tax |
|
10
|
44
|
29
|
129
|
| Gains and Losses on Cash Flow Hedges | Amounts Reclassified from Accumulated Other Comprehensive Loss |
|
|
|
|
|
| Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |
|
|
|
|
|
| Total, pre-tax |
|
16
|
69
|
47
|
203
|
| Tax benefit |
|
(6)
|
(25)
|
(18)
|
(74)
|
| Total, net of tax |
|
10
|
44
|
29
|
129
|
| Gains and Losses on Cash Flow Hedges | Interest Rate Derivatives | Amounts Reclassified from Accumulated Other Comprehensive Loss |
|
|
|
|
|
| Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |
|
|
|
|
|
| Interest charges |
[1] |
16
|
69
|
47
|
203
|
| Amortization of net loss | Amounts Reclassified from Accumulated Other Comprehensive Loss |
|
|
|
|
|
| Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |
|
|
|
|
|
| Total, pre-tax |
[2] |
24
|
0
|
72
|
0
|
| Defined Benefit Pension and Postretirement Items |
|
|
|
|
|
| Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |
|
|
|
|
|
| Total amounts reclassified, net of tax |
|
16
|
0
|
46
|
0
|
| Defined Benefit Pension and Postretirement Items | Amounts Reclassified from Accumulated Other Comprehensive Loss |
|
|
|
|
|
| Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |
|
|
|
|
|
| Total, pre-tax |
|
24
|
0
|
72
|
0
|
| Tax benefit |
|
(8)
|
0
|
(26)
|
0
|
| Total amounts reclassified, net of tax |
|
$ 16
|
$ 0
|
$ 46
|
$ 0
|
|
|