Employee Benefit Plans (Detail) - Profit Sharing Plan - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Profit Sharing Plan [Line Items]
Profit sharing expense		$ 31,852	$ 27,245	$ 26,119
Company dividends received by the Profit Sharing Plan		$ 466	$ 428	$ 159
Company shares held by the Profit Sharing Plan at the end of the year:
Number of shares		1,277,567	1,364,558	1,426,708
Fair value		$ 23,546	$ 23,348	$ 25,010
Profit Sharing Expense
Profit Sharing Plan [Line Items]
Profit sharing expense	[1]	$ 6,919	$ 6,354	$ 2,914

[1] Included in retirement and other employee benefits in the Consolidated Statements of Income