Common Stock and Share-Based Compensation - Summary of Restricted Stock Unit Activity (Detail) (Restricted Stock Units (RSUs), USD $)	9 Months Ended
	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at January 1, 2014	776,290
Stock units issued	403,788
Shares issued upon vesting of stock units	(223,851)
Stock units canceled or forfeited	(183,882)	[1]
Outstanding at September 30, 2014	772,345
Weighted average grant date fair value	$ 14.52
Employees
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at January 1, 2014	680,017
Stock units issued	344,421
Shares issued upon vesting of stock units	(181,570)
Stock units canceled or forfeited	(183,102)	[1]
Outstanding at September 30, 2014	659,766
Weighted average grant date fair value	$ 14.64
Director
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at January 1, 2014	96,273	[2]
Stock units issued	59,367	[2]
Shares issued upon vesting of stock units	(42,281)	[2]
Stock units canceled or forfeited	(780)	[1],[2]
Outstanding at September 30, 2014	112,579	[2]
Weighted average grant date fair value	$ 13.75	[2]

[1] Pursuant to the terms of our stock unit plans, employees have the option of forfeiting stock units to cover their minimum statutory tax withholding when shares are issued. Any stock units surrendered or canceled in satisfaction of participants’ tax withholding obligations are not available for future grants under the plans.

[2] Directors' stock units include Restricted Stock Awards ("RSAs"), which participate in declared dividends.