Long-Term Stock Incentive Plans - Narrative (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Long-Term Stock Incentive Plans:
Weighted average remaining contractual term of stock options outstanding, years	4 years 3 months 18 days	5 years 2 months 12 days
Weighted average remaining contractual term of stock options exercisable, years	4 years	4 years 6 months
Total unrecognized compensation cost related to nonvested share-based compensation awards		$ 3.1
Total unrecognized compensation cost related to nonvested share-based compensation awards weighted average recognition period, years		1 year
Stock Options
Long-Term Stock Incentive Plans:
Long-term stock compensation - vesting period	4 years
Long-term stock compensation - vesting installments	4 years
Long-term stock compensation - minimum contractual term	5 years
Long-term stock compensation - maximum contractual term	10 years
Equity Incentive Plan 2010
Long-Term Stock Incentive Plans:
Long-term stock compensation - ceiling shares	25,000,000
The Prior Plan | Minimum
Long-Term Stock Incentive Plans:
Long-term stock compensation - ceiling shares	500,000
Long-term stock compensation - granting of options authorized, percent of diluted outstanding common stock	9.50%
The Prior Plan | Maximum
Long-Term Stock Incentive Plans:
Long-term stock compensation - ceiling shares	8,932,921