Stock-Based Compensation - Narrative (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($) vesting_type yr shares	Mar. 31, 2016 USD ($) shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of award vesting types | vesting_type	2
Cash liability for performance-based units | $	$ 0.0
Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense | $	$ 0.2	$ 0.2
Stock-based compensation, maximum number of unvested shares (in shares) | shares	344,000
Service Based Award
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options, forfeitures in period (in shares) | shares	0	8,000
Stock-based compensation expense | $	$ 0.0	$ 0.0
Vesting period (in years)	4 years
Expiration period (in years)	8 years
Options issued (in shares) | shares	0	1,000
Deferred Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
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 (in years)	1 year
Minimum age required for meeting directors fees deferred vest criteria | yr	65
Deferred Stock Units | Director
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares issued to non-employee individual (in shares) | shares	4,000	5,000
Deferred stock units, performance-based stock units and restricted stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense | $	$ 0.1	$ 0.6