Legal Proceedings - Additional Information (Detail) (USD $)	0 Months Ended
	Jun. 13, 2014	Jun. 30, 2014
Loss Contingencies [Line Items]
Loss contingency accrual		$ 23,000,000
Estimate of possible losses		51,000,000
Effect of the Court's decision	On June 13, 2014, the Court reversed the court of appeals judgment, the effect of which is that we are no longer liable for the jury verdict and punitive damages award.
Keystone
Loss Contingencies [Line Items]
Loss contingency accrual		69,000,000
Escrow reserve		25,000,000
Other Litigation Cases | Individual Counterparty
Loss Contingencies [Line Items]
Maximum exposure of litigation		$ 150,000