Preferred and Common Stock - Schedule of Options Fully Vested and/or Expected to Vest (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Schedule Of Stock Options [Line Items]
Options Fully Vested and/or Expected to Vest, Number of options	45.0
Options Fully Vested and/or Expected to Vest, Weighted average remaining contractual life, years	4 years 8 months 9 days
Options Fully Vested and/or Expected to Vest, Weighted average exercise price	$ 12.58
Options Fully Vested and/or Expected to Vest, Intrinsic value	$ 7
$6.12 - $8.33 [Member]
Schedule Of Stock Options [Line Items]
Options Fully Vested and/or Expected to Vest, Number of options	17.9
Options Fully Vested and/or Expected to Vest, Weighted average remaining contractual life, years	2 years 22 days
Options Fully Vested and/or Expected to Vest, Weighted average exercise price	$ 8.33
Options Fully Vested and/or Expected to Vest, Intrinsic value	$ 7
Range of exercise price, lower unit	$ 6.12
Range of exercise price, upper unit	$ 8.33
$8.34 - $11.33 [Member]
Schedule Of Stock Options [Line Items]
Options Fully Vested and/or Expected to Vest, Number of options	10.3
Options Fully Vested and/or Expected to Vest, Weighted average remaining contractual life, years	8 years 11 months 5 days
Options Fully Vested and/or Expected to Vest, Weighted average exercise price	$ 10.17
Range of exercise price, lower unit	$ 8.34
Range of exercise price, upper unit	$ 11.33
$11.34 - $17.40 [Member]
Schedule Of Stock Options [Line Items]
Options Fully Vested and/or Expected to Vest, Number of options	11.2
Options Fully Vested and/or Expected to Vest, Weighted average remaining contractual life, years	7 years 2 months 16 days
Options Fully Vested and/or Expected to Vest, Weighted average exercise price	$ 14.47
Range of exercise price, lower unit	$ 11.34
Range of exercise price, upper unit	$ 17.40
$17.41 - $46.77 [Member]
Schedule Of Stock Options [Line Items]
Options Fully Vested and/or Expected to Vest, Number of options	5.6
Options Fully Vested and/or Expected to Vest, Weighted average remaining contractual life, years	3 months 4 days
Options Fully Vested and/or Expected to Vest, Weighted average exercise price	$ 26.96
Range of exercise price, lower unit	$ 17.41
Range of exercise price, upper unit	$ 46.77