Stock-Based Compensation - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended						1 Months Ended				12 Months Ended
	Dec. 31, 2012 M	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2007	Dec. 31, 2012 PSUs [Member]	Apr. 30, 2009 Long-Term Incentive Plan 2009-2011 [Member]	Mar. 31, 2010 Long-Term Incentive Plan 2010-2012 [Member]	Dec. 31, 2011 Long-Term Incentive Plan 2011- 2013 [Member]	Feb. 29, 2012 Long-Term Incentive Plan 2012- 2014 [Member]	Dec. 31, 2012 Performance stock units [Member] M	Dec. 31, 2011 Performance stock units [Member]	Dec. 31, 2010 Performance stock units [Member]	Dec. 31, 2012 Restricted stock units [Member] M	Dec. 31, 2011 Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum expected term of options under incentive compensation plans	10 years
Stock options which vest							One-third each year	One-third each year	One-third each year	One-third each year
Performance stock units granted	589,934		244,043	545,930	283,254	307,813	1,155,000	303,120	311,670	589,934				6,000
Weighted average fair value units, granted	$ 7.33	$ 11.57	$ 9.01								$ 15.63	$ 22.97	$ 18.71	$ 15.54	$ 23.68
Stock options exercisable over the next twelve months	375,270
Weighted average remaining contractual life of options outstanding	7 years 2 months 12 days
Unvested compensation cost related to stock options	$ 4,627										$ 1,743			$ 1,738
Unvested compensation cost related to restricted stock options recognized as expense	21										20			21
Vesting period for restricted stock units, granted	Three to four
Number of vested restricted stock units														96,500	103,834
Performance stock unit vested in period			183,961			91,190					154,129			80,347
Performance stock unit expected to vest		60,082
Performance stock unit expected to vest						84,401
Performance stock unit expected to vest						132,222
Excess tax benefits	$ 2,469	$ 349	$ 3,294