Employee Benefit Plans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Employee Benefit Plans
Maximum contribution by employee (as a percent)			50.00%
Percentage of employer contribution of first 6 percent of covered compensation			50.00%
Maximum employee contribution matched by employer as a percentage of covered compensation			6.00%
Profit sharing and matching contribution expense	$ 6,400	$ 6,100	$ 18,700	$ 16,800
Percentage of incentive compensation	100.00%		100.00%
Net deferred compensation expense	$ 37	$ 100	$ 400	$ 600