Retirement Plans and Other Post-Retirement Benefits - Schedule of Fair Value of Benefit Plan Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 610.7	$ 594.9
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	153.2	233.5
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	457.5	361.4
Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	201.9	175.1
Large Cap [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7.1	58.4
Large Cap [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	194.8	116.7
Small and Mid Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50.9	68.7
Small and Mid Cap [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50.9	68.7
International Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	79.5	79.8
International Equity [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.8	42.2
International Equity [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40.7	37.6
Real Estate Investment Trusts (REIT) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27.9	31.9
Real Estate Investment Trusts (REIT) [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27.9	31.9
Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	237.7	222.4
Fixed Income [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28.5	32.3
Fixed Income [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	209.2	190.1
Cash and Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12.8	17.0
Cash and Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 12.8	$ 17.0