Retirement Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Benefits Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	100.00%	100.00%	100.00%
Employees contribution to 401(k) plan that is 100 % matched by employer	4.00%	4.00%	4.00%
Defined Contribution Plan, employer discretionary matching contribution percent	2.00%	0.00%	0.00%
Defined Contribution Plan, employer discretionary matching contribution amount	$ 800,000	$ 0	$ 0
401(k) plan expense	5,100,000	4,600,000	1,600,000
Retirement Savings Contributions
Employee Benefits Disclosure [Line Items]
401(k) plan expense	2,700,000	2,500,000
Non Discretionary Matching Contributions
Employee Benefits Disclosure [Line Items]
401(k) plan expense	1,600,000	2,100,000
Money Purchase Defined Contribution Plan
Employee Benefits Disclosure [Line Items]
401(k) plan expense			2,800,000
Maximum
Employee Benefits Disclosure [Line Items]
Discretion of contribution to each eligible employee's 401(k) plan irrespective of the employees' contribution	4.00%
United States
Employee Benefits Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	7.50%
Defined contribution plan employees vesting percentage beginning at the end of their second year	20.00%
Defined contribution plan additional employees vesting percentage being fully vested	6 years
United States | Maximum
Employee Benefits Disclosure [Line Items]
Bonus to employees			2,500
United Kingdom
Employee Benefits Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	15.00%
401(k) plan expense	$ 2,200,000	$ 1,900,000	$ 1,700,000