Unvested RSAs by Grant-Date Fair Value (Detail) (Restricted Stock) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of SARs Outstanding at Year End	7,253	6,710	6,379	4,764
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Outstanding Weighted Average Remaining Contractual Terms	1 year 4 months 24 days
$5.01-$10.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of SARs Outstanding at Year End	48
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Outstanding Weighted Average Remaining Contractual Terms	0 years 9 months 18 days
$10.01-$15.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of SARs Outstanding at Year End	1,801
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Outstanding Weighted Average Remaining Contractual Terms	0 years 8 months 12 days
$15.01-$20.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of SARs Outstanding at Year End	2,320
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Outstanding Weighted Average Remaining Contractual Terms	1 year 3 months 18 days
$20.01-$25.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of SARs Outstanding at Year End	3,084
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Outstanding Weighted Average Remaining Contractual Terms	1 year 9 months 18 days