Employee Benefit Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Discretionary contribution amount	$ 0	$ 0	$ 0
U.S. Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage to defer up base compensation of employees, effective from January 1, 2006	25.00%
Amount to defer up bonus compensation of employees, effective from January 1, 2006	$ 500,000
Percentage to defer up eligible bonus compensation, effective from January 1, 2006		25.00%
Amount of compensation deferred in plan	$ 14,900,000	$ 12,000,000
Percentage to defer up cash component of director's fees for non-employee [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage to defer up directors' fees	100.00%
Non-Employee Directors Voluntary Deferred Compensation Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Amount of compensation deferred in plan	$ 2,400,000	2,100,000
Qualified Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage for employee pre-tax and/or after-tax contributions, minimum	1.00%
Percentage for employee pre-tax and/or after-tax contributions, maximum	50.00%
Minimum amount of employee contributions	$ 6,000	$ 5,500	$ 5,000
Percentage of eligible compensation	6.00%	5.50%	5.00%
Eligible service period for company match	1 year
Defined Contribution Plan, Cost Recognized	$ 4,800,000	$ 3,300,000	$ 2,800,000