Employee Benefit Plans - Aggregate Fair Value of CMRT Assets (Detail) - CMRT - USD ($)
$ in Millions |
Dec. 31, 2016 |
Dec. 31, 2015 |
| Defined Benefit Plan Disclosure [Line Items] |
|
|
| CMRT asset value |
$ 637.8
|
$ 648.8
|
| Assets not subject to fair value hierarchy |
30.00%
|
30.00%
|
| Total percentage of CMRT assets |
100.00%
|
100.00%
|
| Asset allocation percentage |
100.00%
|
100.00%
|
| Equities Principally Publicly Traded | United States |
|
|
| Defined Benefit Plan Disclosure [Line Items] |
|
|
| Asset allocation percentage |
31.00%
|
29.00%
|
| Equities Principally Publicly Traded | Non-US |
|
|
| Defined Benefit Plan Disclosure [Line Items] |
|
|
| Asset allocation percentage |
22.00%
|
22.00%
|
| Fixed Income Securities, Principally Publically Traded |
|
|
| Defined Benefit Plan Disclosure [Line Items] |
|
|
| Asset allocation percentage |
36.00%
|
38.00%
|
| Privately Managed Limited Partnerships |
|
|
| Defined Benefit Plan Disclosure [Line Items] |
|
|
| Asset allocation percentage |
5.00%
|
5.00%
|
| Hedge Funds |
|
|
| Defined Benefit Plan Disclosure [Line Items] |
|
|
| Asset allocation percentage |
5.00%
|
5.00%
|
| Other, Primarily Cash |
|
|
| Defined Benefit Plan Disclosure [Line Items] |
|
|
| Asset allocation percentage |
1.00%
|
1.00%
|
| Level 1 |
|
|
| Defined Benefit Plan Disclosure [Line Items] |
|
|
| Assets subject to fair value hierarchy |
54.00%
|
54.00%
|
| Level 2 |
|
|
| Defined Benefit Plan Disclosure [Line Items] |
|
|
| Assets subject to fair value hierarchy |
8.00%
|
7.00%
|
| Level 3 |
|
|
| Defined Benefit Plan Disclosure [Line Items] |
|
|
| Assets subject to fair value hierarchy |
8.00%
|
9.00%
|