Employee Benefit Plans - Additional Information (Detail)			9 Months Ended
	Sep. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2014 2014 Through 2020 [Member] GBP (£)	Sep. 30, 2014 2012 Through 2020 [Member] United Kingdom [Member] Pension Plans [Member] GBP (£)
Defined Benefit Plan Disclosure [Line Items]
Additional contribution to plan assets				£ 1,000,000
Additional contribution to escrow account			1,000,000
Aggregate amount in account security arrangement	$ 18,200,000	$ 16,900,000