Income Taxes - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Tax Credit Carryforward [Line Items]
Operating loss carryforward	$ 6,059,276
Operating tax carryforward expiration year start	2029
Operating tax carryforward expiration year end	2034
U. S. Federal Net Operating Tax [Member]
Tax Credit Carryforward [Line Items]
Net operating tax carryforward	5,340,692
United States [Member]
Tax Credit Carryforward [Line Items]
Operating loss carryforward	528,846
United Kingdom [Member]
Tax Credit Carryforward [Line Items]
Operating loss carryforward	$ 189,738