Employee Stock and Incentive Plans - Performance Shares and Restricted Stock Units (Details) - USD ($)
$ / shares in Units, $ in Millions |
1 Months Ended |
12 Months Ended |
Feb. 29, 2020 |
Jan. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
| Performance Shares [Member] |
|
|
|
|
|
|
| Stock-based Compensation [Line Items] |
|
|
|
|
|
|
| Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition |
|
|
|
1 year 7 months 6 days
|
|
|
| Number of Shares [Rollforward] |
|
|
|
|
|
|
| As of January 1 |
|
|
99,585
|
129,693
|
127,898
|
127,580
|
| Granted |
[1] |
|
|
60,747
|
66,557
|
50,729
|
| Awarded |
|
|
|
(75,943)
|
(58,293)
|
0
|
| Unearned Grant Award |
|
|
|
0
|
0
|
(40,801)
|
| Forfeited |
|
|
|
(14,912)
|
(6,469)
|
(9,610)
|
| As of December 31 |
|
|
|
99,585
|
129,693
|
127,898
|
| Performance Period (Years) |
|
|
|
3 years
|
|
|
| Weighted-Average Grant Date Fair Value [Abstract] |
|
|
|
|
|
|
| As of January 1 |
|
|
$ 72.78
|
$ 66.12
|
$ 58.23
|
$ 52.56
|
| Granted |
[1] |
|
|
63.89
|
76.42
|
62.90
|
| Awarded |
|
|
|
53.44
|
59.82
|
0
|
| Unearned Grant Award |
|
|
|
0
|
0
|
46.27
|
| Forfeited |
|
|
|
77.14
|
72.99
|
58.29
|
| As of December 31 |
|
|
|
$ 72.78
|
$ 66.12
|
$ 58.23
|
| Restricted Stock Units [Member] |
|
|
|
|
|
|
| Number of Shares [Rollforward] |
|
|
|
|
|
|
| As of January 1 |
|
|
39,943
|
49,771
|
55,248
|
54,728
|
| Granted |
[2] |
|
|
13,927
|
16,573
|
21,241
|
| Awarded |
|
|
|
(21,110)
|
(18,881)
|
(17,281)
|
| Forfeited |
|
|
|
(2,645)
|
(3,169)
|
(3,440)
|
| As of December 31 |
|
|
|
39,943
|
49,771
|
55,248
|
| Performance Period (Years) |
|
|
|
3 years
|
|
|
| Weighted-Average Grant Date Fair Value [Abstract] |
|
|
|
|
|
|
| As of January 1 |
|
|
$ 69.30
|
$ 60.74
|
$ 56.18
|
$ 51.79
|
| Granted |
[2] |
|
|
74.93
|
71.11
|
62.20
|
| Awarded |
|
|
|
52.44
|
55.78
|
49.72
|
| Forfeited |
|
|
|
72.43
|
64.92
|
56.00
|
| As of December 31 |
|
|
|
$ 69.30
|
$ 60.74
|
$ 56.18
|
| Subsequent Event [Member] | Performance Shares [Member] |
|
|
|
|
|
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| Number of Shares [Rollforward] |
|
|
|
|
|
|
| Granted |
|
|
22,000
|
|
|
|
| Awarded |
|
(25,000)
|
|
|
|
|
| Performance Period (Years) |
|
|
3 years
|
|
|
|
| Granted, Grant Date Fair Value |
|
|
$ 1.8
|
|
|
|
| Awarded, Grant Date Fair Value |
|
$ 1.6
|
|
|
|
|
| Subsequent Event [Member] | Restricted Stock Units [Member] |
|
|
|
|
|
|
| Number of Shares [Rollforward] |
|
|
|
|
|
|
| Granted |
|
|
14,000
|
|
|
|
| Awarded |
|
(15,000)
|
|
|
|
|
| Granted, Grant Date Fair Value |
|
|
$ 1.1
|
|
|
|
| Awarded, Grant Date Fair Value |
|
$ 0.9
|
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