Stock-Based Compensation - Narrative (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Market Based Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period			8 years
Options vested			0	0
Stock-based compensation expense	$ 0	$ 0.1	$ 0.2	$ 0.3
Stock-based compensation, maximum number of unvested shares			457,000
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures and Expirations		499,000
Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	0.1	0	0.3	0.1
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures and Expirations			16,000	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period			0	14,000
Performance based maximum number of unvested shares			795,000
Service Based Award [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	0.2	0.1	0.4	0.5
Vesting period			4 years
Expiration term			8 years
Options issued			39,000	46,000
Deferred Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Deferred stock units issued to non-employee directors			46,000	23,000
Percentage of shares vested in lieu of directors fees at the grant date			100.00%
Portion of Director fees matched to deferred stock units			25.00%
Vesting period of deferred stock			1 year
Minimum age required for meeting directors fees deferred vest criteria			65 years
Deferred stock units, performance-based stock units and restricted stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	0.3	0.1	1.0	0.6
Unrestricted Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense				$ 0.1
Share based compensation arrangement by share based payment award equity instruments other than options issued in period				5