Accumulated Other Comprehensive Income - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Amounts reclassified out of accumulated other comprehensive income related to defined benefit pension plans as component of net periodic benefit cost, actuarial net loss	$ 0.4	$ 0.2	$ 0.8	$ 0.4