Employee Benefit and Retirement Plans - Composition of Domestic Pension Plan Assets (Detail) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 |
United States Pension Plan of US Entity [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | $ 1,271.1 | $ 1,230.6 | |
United States Pension Plan of US Entity [Member] | Fair Value [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 842.9 | 674.3 | |
United States Pension Plan of US Entity [Member] | Portion at Other than Fair Value Measurement [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 428.2 | 556.3 | |
United States Pension Plan of US Entity [Member] | Equity Securities [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 134.5 | 270.4 | |
United States Pension Plan of US Entity [Member] | Equity Securities [Member] | Fair Value [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 129.8 | 149.8 | |
United States Pension Plan of US Entity [Member] | Equity Securities [Member] | Portion at Other than Fair Value Measurement [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 4.7 | 120.6 | |
United States Pension Plan of US Entity [Member] | International Equity [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 159.8 | 181.6 | |
United States Pension Plan of US Entity [Member] | International Equity [Member] | Fair Value [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 75.5 | 80.4 | |
United States Pension Plan of US Entity [Member] | International Equity [Member] | Portion at Other than Fair Value Measurement [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 84.3 | 101.2 | |
United States Pension Plan of US Entity [Member] | Fixed Income Securities [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 602.9 | 583.7 | |
United States Pension Plan of US Entity [Member] | Fixed Income Securities [Member] | Fair Value [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 395.4 | 372.7 | |
United States Pension Plan of US Entity [Member] | Fixed Income Securities [Member] | Portion at Other than Fair Value Measurement [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 207.5 | 211 | |
United States Pension Plan of US Entity [Member] | Alternative Investments [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 173.7 | 166.1 | |
United States Pension Plan of US Entity [Member] | Alternative Investments [Member] | Fair Value [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 42 | 42.6 | |
United States Pension Plan of US Entity [Member] | Alternative Investments [Member] | Portion at Other than Fair Value Measurement [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 131.7 | 123.5 | |
United States Pension Plan of US Entity [Member] | Cash and Other Investments [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 200.2 | 28.8 | |
United States Pension Plan of US Entity [Member] | Cash and Other Investments [Member] | Fair Value [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 200.2 | 28.8 | |
Level 1 [Member] | United States Pension Plan of US Entity [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 808.4 | 638.9 | |
Level 1 [Member] | United States Pension Plan of US Entity [Member] | Equity Securities [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 129.8 | 149.8 | |
Level 1 [Member] | United States Pension Plan of US Entity [Member] | International Equity [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 75.5 | 80.4 | |
Level 1 [Member] | United States Pension Plan of US Entity [Member] | Fixed Income Securities [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 395.4 | 372.7 | |
Level 1 [Member] | United States Pension Plan of US Entity [Member] | Alternative Investments [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 23.8 | 23.5 | |
Level 1 [Member] | United States Pension Plan of US Entity [Member] | Cash and Other Investments [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 183.9 | 12.5 | |
Level 2 [Member] | United States Pension Plan of US Entity [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 15.2 | 15.2 | |
Level 2 [Member] | United States Pension Plan of US Entity [Member] | Cash and Other Investments [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 15.2 | 15.2 | |
Level 3 [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 33 | 39 | $ 26.9 |
Level 3 [Member] | United States Pension Plan of US Entity [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 19.3 | 20.2 | |
Level 3 [Member] | United States Pension Plan of US Entity [Member] | Alternative Investments [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | 18.2 | 19.1 | |
Level 3 [Member] | United States Pension Plan of US Entity [Member] | Cash and Other Investments [Member] | | | |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] | | | |
Defined benefit plan, fair value of plan assets | $ 1.1 | $ 1.1 | |