Capital and Regulatory Matters (Tables)

12 Months Ended

Dec. 31, 2018

Regulatory Capital Requirements [Abstract]

Actual and Required Capital Ratios

	Actual				Minimum Capital Required - Basel III Phase-In Schedule				Minimum Capital Required - Basel III Fully Phased-In				Required to be Considered Well Capitalized
	Capital Amount		Ratio		Capital Amount		Ratio		Capital Amount		Ratio		Capital Amount		Ratio
2018
Common Equity Tier 1 to Risk-Weighted Assets
Cullen/Frost	$	2,642,475	12.65	%	$	1,332,052	6.375	%	$	1,462,645	7.00	%	$	1,358,171	6.50	%
Frost Bank	2,743,973		13.17		1,328,180		6.375		1,458,393		7.00		1,354,222		6.50
Tier 1 Capital to Risk-Weighted Assets
Cullen/Frost	2,786,961		13.34		1,645,476		7.875		1,776,069		8.50		1,671,595		8.00
Frost Bank	2,743,973		13.17		1,640,693		7.875		1,770,906		8.50		1,666,735		8.00
Total Capital to Risk-Weighted Assets
Cullen/Frost	3,152,593		15.09		2,063,375		9.875		2,193,968		10.50		2,089,494		10.00
Frost Bank	2,876,605		13.81		2,057,376		9.875		2,187,590		10.50		2,083,419		10.00
Leverage Ratio
Cullen/Frost	2,786,961		9.06		1,231,028		4.00		1,231,028		4.00		1,538,785		5.00
Frost Bank	2,743,973		8.93		1,229,650		4.00		1,229,650		4.00		1,537,062		5.00
2017
Common Equity Tier 1 to Risk-Weighted Assets
Cullen/Frost	$	2,426,048	12.42	%	$	1,123,430	5.75	%	$	1,367,583	7.00	%	$	1,269,965	6.50	%
Frost Bank	2,518,999		12.92		1,120,663		5.75		1,364,214		7.00		1,266,836		6.50
Tier 1 Capital to Risk-Weighted Assets
Cullen/Frost	2,570,534		13.16		1,416,499		7.25		1,660,637		8.50		1,563,033		8.00
Frost Bank	2,518,999		12.92		1,413,010		7.25		1,656,546		8.50		1,559,183		8.00
Total Capital to Risk-Weighted Assets
Cullen/Frost	2,959,326		15.15		1,807,257		9.25		2,051,375		10.50		1,953,792		10.00
Frost Bank	2,674,791		13.72		1,802,805		9.25		2,046,321		10.50		1,948,979		10.00
Leverage Ratio
Cullen/Frost	2,570,534		8.46		1,215,227		4.00		1,215,186		4.00		1,519,034		5.00
Frost Bank	2,518,999		8.30		1,214,295		4.00		1,214,254		4.00		1,517,869		5.00