v3.7.0.1
Changes in Level 3 Assets (Detail) - Level 3 [Member]
$ in Millions
12 Months Ended
Dec. 31, 2016
USD ($)
Defined Benefit Plan Disclosure [Line Items]  
Beginning fair value of plan assets $ 1.3
Return on plan assets 0.1
Purchases 0.1
Sales (0.1)
Ending fair value of plan assets $ 1.4