Condensed Financial Information of Parent Company - Condensed Statements of Earnings (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Other expense, net									$ (126,229)	$ (114,028)	$ (138,160)
Net earnings	25,581	24,295	(25,484)	28,661	25,288	24,239	24,466	21,615	104,021	95,608	77,280
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Excess in net earnings of subsidiaries									66,119	33,149	(1,261)
Dividends from the Bank									41,000	63,000	82,300
Other expense, net									(3,098)	(541)	(3,759)
Net earnings									$ 104,021	$ 95,608	$ 77,280