Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax [Line Items]
Income before income taxes	$ 42.6	$ 51.8	$ 51.0
Undistributed earnings	113
Employee post-retirement benefit plans	2.2	(9.3)	(0.8)
Income tax benefit related to restricted stock and stock options	1.6		0.2
Valuation allowance, operating loss carryforwards	7.1
Valuation allowance, capital loss	1.5
Net operating losses	9.4	11.2
Expiration of foreign tax credits	2018
Valuation allowance on foreign tax credits	8.8
Unrecognized tax benefits	5.5	7.1
Interest expense and related penalties	0.3	0.2	0.2
Accrued interest expense and penalties	1.3	0.9
State [Member]
Income Tax [Line Items]
Net operating losses	9.2
Operating losses expiration	2014 to 2030
Foreign [Member]
Income Tax [Line Items]
Net operating losses	$ 0.2
Operating losses expiration	2019