Income Taxes - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Tax Credit Carryforward [Line Items]
Operating loss carryforward	$ 6,079,936
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	5,195,425
United States [Member]
Tax Credit Carryforward [Line Items]
Operating loss carryforward	577,742
United Kingdom [Member]
Tax Credit Carryforward [Line Items]
Operating loss carryforward	$ 306,769