Operating Segments - Summary of Operating Results by Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Revenues from (expenses to) external customers	$ 248,779	$ 225,690	$ 486,604	$ 456,283
Net income	66,470	59,663	127,658	114,851
Operating Segments [Member] | Banking [Member]
Segment Reporting Information [Line Items]
Revenues from (expenses to) external customers	216,258	198,206	422,472	402,466
Net income	63,872	56,582	119,928	110,135
Operating Segments [Member] | Frost Wealth Advisors [Member]
Segment Reporting Information [Line Items]
Revenues from (expenses to) external customers	32,313	28,259	63,407	55,482
Net income	5,388	4,263	10,472	7,501
Operating Segments [Member] | Non-Banks [Member]
Segment Reporting Information [Line Items]
Revenues from (expenses to) external customers	208	(775)	725	(1,665)
Net income	$ (2,790)	$ (1,182)	$ (2,742)	$ (2,785)