Unvested RSAs by Grant-Date Fair Value (Detail) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSAs at Year End	4,764
Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSAs at Year End	4,764	5,158	4,645	5,584
Weighted-Average Remaining Contractual Life (in years)	1.3
Under $10.00 | Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSAs at Year End	409
Weighted-Average Remaining Contractual Life (in years)	1.3
$10.01-$20.00 | Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSAs at Year End	3,982
Weighted-Average Remaining Contractual Life (in years)	1.4
$20.01-$30.00 | Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSAs at Year End	134
Weighted-Average Remaining Contractual Life (in years)	0.3
$30.01-$40.00 | Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSAs at Year End	239
Weighted-Average Remaining Contractual Life (in years)	0.3