Capital and Regulatory Matters (Tables)

12 Months Ended

Dec. 31, 2017

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
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
2016
Common Equity Tier 1 to Risk-Weighted Assets
Cullen/Frost	$	2,239,186	12.52	%	$	916,360	5.125	%	$	1,251,425	7.00	%	$	1,162,213	6.50	%
Frost Bank	2,296,480		12.88		913,460		5.125		1,247,463		7.00		1,158,535		6.50
Tier 1 Capital to Risk-Weighted Assets
Cullen/Frost	2,383,672		13.33		1,184,563		6.625		1,519,587		8.50		1,430,416		8.00
Frost Bank	2,296,480		12.88		1,180,814		6.625		1,514,776		8.50		1,425,889		8.00
Total Capital to Risk-Weighted Assets
Cullen/Frost	2,669,717		14.93		1,542,168		8.625		1,877,137		10.50		1,788,020		10.00
Frost Bank	2,449,525		13.74		1,537,286		8.625		1,871,194		10.50		1,782,361		10.00
Leverage Ratio
Cullen/Frost	2,383,672		8.14		1,171,682		4.00		1,171,573		4.00		1,464,602		5.00
Frost Bank	2,296,480		7.85		1,170,249		4.00		1,170,141		4.00		1,462,812		5.00