Items Measured at Fair Value on a Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets (Note 14)	$ 2.4	$ 0.8
Total assets	211.8	173.4
Derivative liabilities (Note 14)	1.0	4.1
Total liabilities	31.9	29.7
Bank time deposits with original maturities of three months or less | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank time deposits with original maturities of three months or less	178.3	145.8
Diversified investments associated with the Executive Stock Unit Program (ESUP) | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Diversified investments associated with the Executive Stock Unit Program (ESUP)	31.1	26.8
Liabilities Associated With Esup | Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities	30.9	25.6
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets (Note 14)	0.0	0.0
Total assets	31.1	26.8
Derivative liabilities (Note 14)	0.0	0.0
Total liabilities	30.9	25.6
Level 1 | Bank time deposits with original maturities of three months or less
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank time deposits with original maturities of three months or less	0.0	0.0
Level 1 | Diversified investments associated with the Executive Stock Unit Program (ESUP)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Diversified investments associated with the Executive Stock Unit Program (ESUP)	31.1	26.8
Level 1 | Liabilities Associated With Esup
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities	30.9	25.6
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets (Note 14)	2.4	0.8
Total assets	180.7	146.6
Derivative liabilities (Note 14)	1.0	4.1
Total liabilities	1.0	4.1
Level 2 | Bank time deposits with original maturities of three months or less
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank time deposits with original maturities of three months or less	178.3	145.8
Level 2 | Diversified investments associated with the Executive Stock Unit Program (ESUP)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Diversified investments associated with the Executive Stock Unit Program (ESUP)	0.0	0.0
Level 2 | Liabilities Associated With Esup
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities	0.0	0.0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets (Note 14)	0.0	0.0
Total assets	0.0	0.0
Derivative liabilities (Note 14)	0.0	0.0
Total liabilities	0.0	0.0
Level 3 | Bank time deposits with original maturities of three months or less
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank time deposits with original maturities of three months or less	0.0	0.0
Level 3 | Diversified investments associated with the Executive Stock Unit Program (ESUP)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Diversified investments associated with the Executive Stock Unit Program (ESUP)	0.0	0.0
Level 3 | Liabilities Associated With Esup
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities	$ 0.0	$ 0.0