Employee Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011 Age
Defined Benefit Plan Disclosure [Line Items]
Estimated contribution defined contribution plans	$ 46.8	$ 43.0	$ 41.0
Rabbi Trust
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan	93.2	85.1
Contributions made to the pension plan	13.9	16.4
U.S. Plan
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan	1,440.8	1,342.1	1,277.7
Prior service costs, amortization period (years)	11 years
Benefit Obligation increase as a result of adopting the RP-2014 mortality table with improvement scale MP-2014	25.7
Expected long-term rate of return on plan assets	7.25%
Weighted average discount rate used in determining the accumulated postretirement benefit obligation	4.25%	5.00%
U.S. Plan | Alternative Investment
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets	20.00%
U.S. Plan | Qualified Defined Benefit Pension Plans | Lower Limit
Defined Benefit Plan Disclosure [Line Items]
Contribution to plan assets	0
U.S. Plan | Qualified Defined Benefit Pension Plans | Upper Limit
Defined Benefit Plan Disclosure [Line Items]
Contribution to plan assets	150.0
U.S. Plan | U.S. | Preferred and Common Stock
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan		116.0
Target allocation of plan assets	20.00%
U.S. Plan | Non U.S. | Preferred and Common Stock
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan		56.8
Target allocation of plan assets	15.00%
U.S. Plan | U.S. Government Sponsored Agency | Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets	45.00%
U.S. Plan | Private Equity Funds | Alternative Investment
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets	5.00%
U.S. Plan | Private Equity Funds | Upper Limit
Defined Benefit Plan Disclosure [Line Items]
Equity target allocation of plan assets	20.00%
U.S. Plan | Hedge Funds | Alternative Investment
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets	5.00%
U.S. Plan | Real Estate | Alternative Investment
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets	5.00%
U.S. Plan | Global Listed Infrastructure | Alternative Investment
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets	5.00%
U.S. Plan | Derivative Financial Instruments, Assets
Defined Benefit Plan Disclosure [Line Items]
Assets related to the pension plan	0	0
Supplemental Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service costs, amortization period (years)	9 years
Benefit Obligation increase as a result of adopting the RP-2014 mortality table with improvement scale MP-2014	0.7
Weighted average discount rate used in determining the accumulated postretirement benefit obligation	4.25%	5.00%
Defined Benefit Postretirement Health Coverage
Defined Benefit Plan Disclosure [Line Items]
Services attained by employees for eligibility, years				15 years
Services attained by employees for eligibility, retiring age				55
Employee Group Waiver Plan
Defined Benefit Plan Disclosure [Line Items]
Employee Group Waiver Plan (EGWP), effective date	January 2012
Reduction in postretirement health care plan liability			26.7
Increase in net actuarial gain			3.3
Other Postretirement Plan
Defined Benefit Plan Disclosure [Line Items]
Benefit Obligation increase as a result of adopting the RP-2014 mortality table with improvement scale MP-2014	2.2
Weighted average discount rate used in determining the accumulated postretirement benefit obligation	4.25%	5.00%
Ultimate health care rate	5.00%
Other Postretirement Plan | Pre-Age 65 Medical and Drug Benefits
Defined Benefit Plan Disclosure [Line Items]
Current health care cost trend rate	8.00%
Year in which ultimate trend rate will be reached	2022
Other Postretirement Plan | Post-Age 65 Medical and Drug Benefits
Defined Benefit Plan Disclosure [Line Items]
Current health care cost trend rate	7.50%
Year in which ultimate trend rate will be reached	2022
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Amortization from AOCI of the net actuarial gain (loss)	38.6
Amortization from AOCI of the prior service benefit	$ (0.2)