Stock-Based Employee Benefit Plans - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended						3 Months Ended		9 Months Ended				1 Months Ended								9 Months Ended		1 Months Ended	9 Months Ended		1 Months Ended	9 Months Ended				1 Months Ended	9 Months Ended		1 Months Ended
	Sep. 30, 2013 Nonqualified Stock Option Plan	Sep. 30, 2012 Nonqualified Stock Option Plan	Sep. 30, 2013 Nonqualified Stock Option Plan	Sep. 30, 2012 Nonqualified Stock Option Plan	Sep. 30, 2013 Nonqualified Stock Option Plan Historical Volatility	Sep. 30, 2013 Nonqualified Stock Option Plan Implied Volatility	Sep. 30, 2012 Nonqualified Stock Option Plan One Year After Grant	Sep. 30, 2012 Nonqualified Stock Option Plan Two Years After Grant	Sep. 30, 2013 Employee Stock Purchase Plan	Sep. 30, 2012 Employee Stock Purchase Plan	Sep. 30, 2013 Employee Stock Purchase Plan Y M	Sep. 30, 2012 Employee Stock Purchase Plan Y	Sep. 30, 2013 Employee Stock Purchase Plan Historical Volatility	Sep. 30, 2013 Employee Stock Purchase Plan Implied Volatility	Aug. 01, 2013 Employee Stock Purchase Plan Minimum	Feb. 01, 2013 Employee Stock Purchase Plan Minimum	Aug. 01, 2012 Employee Stock Purchase Plan Minimum	Feb. 01, 2012 Employee Stock Purchase Plan Minimum	Aug. 01, 2013 Employee Stock Purchase Plan Maximum	Feb. 01, 2013 Employee Stock Purchase Plan Maximum	Aug. 01, 2012 Employee Stock Purchase Plan Maximum	Feb. 01, 2012 Employee Stock Purchase Plan Maximum	Sep. 30, 2013 Performance Shares Y	Sep. 30, 2012 Performance Shares	Jul. 23, 2013 Performance Shares Interim Chief Executive Officer	Sep. 30, 2013 Performance Shares Minimum	Sep. 30, 2013 Performance Shares Maximum	Jul. 23, 2013 Performance Shares Maximum Interim Chief Executive Officer	Sep. 30, 2013 Restricted Stock Units (RSUs)	Sep. 30, 2012 Restricted Stock Units (RSUs)	Sep. 30, 2013 Restricted Stock Units (RSUs) Non Employee Directors	Sep. 30, 2012 Restricted Stock Units (RSUs) Non Employee Directors	Jul. 23, 2013 Restricted Stock Units (RSUs) Interim Chief Executive Officer	Sep. 30, 2013 Restricted Stock Units (RSUs) Minimum	Sep. 30, 2013 Restricted Stock Units (RSUs) Maximum	Jul. 23, 2013 Restricted Stock Units (RSUs) Maximum Interim Chief Executive Officer
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted				479,571																			1,373,329	1,795,893	98,700				4,571,571	4,432,219	100,000	120,000	98,700
Stock-based compensation expense	$ 100,000	$ 400,000	$ 700,000	$ 600,000					$ 2,400,000	$ 5,400,000	$ 10,300,000	$ 15,300,000
Weighted average estimated fair value of share granted		$ 4.45		$ 4.45											$ 2.60	$ 2.93	$ 2.69	$ 6.43	$ 4.06	$ 4.57	$ 3.96	$ 8.40	$ 8.83	$ 17.21	$ 9.70				$ 10.12	$ 15.48	$ 11.14	$ 10.77	$ 11.18
Non-qualified stock options granted, vesting percentage							50.00%	50.00%
Blended volatility					50.00%	50.00%							50.00%	50.00%
Offering period											2	2
Vesting period (in years)																										1 year	3 years	3 years						1 year	3 years	3 years
Award target performance rate, low																										0.00%
Award target performance rate, high																											150.00%
Number of performance periods																							3
Stock-based compensation expense awards amortization period																															6 months
Maximum percentage of employees' compensation deductions											15.00%
Discount from market price											85.00%
Maximum worth of shares per employee											25,000
Maximum number of shares per employee											10,000
Purchase period, months											6
Share based compensation, number of units approved									5,259,136		5,259,136
Number of shares purchased											2,904,287	1,867,683
Cumulative incremental expenses incurred									$ 1,400,000	$ 6,100,000	$ 7,900,000	$ 20,200,000