Expiration of Loss and Tax Credit Carryforwards (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Operating Loss and Tax Credit Carryforward [Line Items]
Loss carryforwards	$ 869,940
Tax credit carryforwards	72,469
Period of Expiration 2015 - 2019
Operating Loss and Tax Credit Carryforward [Line Items]
Loss carryforwards	251,698
Tax credit carryforwards	25,620
Period of Expiration Thereafter
Operating Loss and Tax Credit Carryforward [Line Items]
Loss carryforwards	376,764
Tax credit carryforwards	42,890
No Expiration Date
Operating Loss and Tax Credit Carryforward [Line Items]
Loss carryforwards	241,478
Tax credit carryforwards	$ 3,959