XML 211 R184.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2
Regulatory Capital Requirements - Risk-Based Capital Amounts and Ratios (Detail) - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Supplementary Leverage Capital [Abstract]    
Supplementary leverage, risk based capital required to be well capitalized to risk weighted assets 3.00%  
STANDARDIZED APPROACH | Parent Company    
Tier 1 Capital    
BALANCE $ 10,152.0 $ 9,596.7
RATIO 14.50% 14.10%
Minimum to qualify as well-capitalized balance $ 4,205.3 $ 4,070.2
Minimum to qualify as well-capitalized ratio 6.00% 6.00%
Total Capital    
BALANCE $ 11,456.7 $ 10,942.0
RATIO 16.30% 16.10%
Minimum to qualify as well-capitalized balance $ 7,008.8 $ 6,783.7
Minimum to qualify as well-capitalized ratio   10.00%
Leverage (Tier 1 Capital to Adjusted Average Fourth Quarter Assets)    
BALANCE $ 10,152.0 $ 9,596.7
RATIO 8.70% 8.00%
STANDARDIZED APPROACH | Parent Company | Common Stock    
Tier 1 Capital    
BALANCE $ 8,898.7 $ 8,729.8
RATIO 12.70% 12.90%
STANDARDIZED APPROACH | The Northern Trust Company    
Tier 1 Capital    
BALANCE $ 8,476.0 $ 8,722.5
RATIO 12.30% 13.10%
Minimum to qualify as well-capitalized balance $ 5,504.0 $ 5,336.4
Minimum to qualify as well-capitalized ratio 8.00% 8.00%
Total Capital    
BALANCE $ 9,610.4 $ 9,870.7
RATIO 14.00% 14.80%
Minimum to qualify as well-capitalized balance $ 6,880.1 $ 6,670.6
Minimum to qualify as well-capitalized ratio 10.00% 10.00%
Leverage (Tier 1 Capital to Adjusted Average Fourth Quarter Assets)    
BALANCE $ 8,476.0 $ 8,722.5
RATIO 7.30% 7.30%
Minimum to qualify as well-capitalized balance $ 5,835.4 $ 5,998.6
Minimum to qualify as well-capitalized ratio 5.00% 5.00%
STANDARDIZED APPROACH | The Northern Trust Company | Common Stock    
Tier 1 Capital    
BALANCE $ 8,476.0 $ 8,722.5
RATIO 12.30% 13.10%
Minimum to qualify as well-capitalized balance $ 4,472.0 $ 4,335.9
Minimum to qualify as well-capitalized ratio 6.50% 6.50%
ADVANCED APPROACH | Parent Company    
Tier 1 Capital    
BALANCE $ 10,152.0 $ 9,596.7
RATIO 15.00% 15.00%
Minimum to qualify as well-capitalized balance $ 4,051.6 $ 3,834.9
Minimum to qualify as well-capitalized ratio 6.00% 6.00%
Total Capital    
BALANCE $ 11,332.3 $ 10,803.8
RATIO 16.80% 16.90%
Minimum to qualify as well-capitalized balance $ 6,752.7 $ 6,391.5
Minimum to qualify as well-capitalized ratio   10.00%
Leverage (Tier 1 Capital to Adjusted Average Fourth Quarter Assets)    
BALANCE $ 10,152.0 $ 9,596.7
RATIO 8.70% 8.00%
Supplementary Leverage Capital [Abstract]    
Supplementary leverage capital $ 10,152.0 $ 9,596.7
Supplementary leverage capital to average assets 7.60% 7.00%
ADVANCED APPROACH | Parent Company | Common Stock    
Tier 1 Capital    
BALANCE   $ 8,729.8
RATIO 13.20% 13.70%
ADVANCED APPROACH | The Northern Trust Company    
Tier 1 Capital    
BALANCE $ 8,476.0 $ 8,722.5
RATIO 13.00% 14.10%
Minimum to qualify as well-capitalized balance $ 5,206.2 $ 4,932.2
Minimum to qualify as well-capitalized ratio 8.00% 8.00%
Total Capital    
BALANCE $ 9,486.0 $ 9,732.5
RATIO 14.60% 15.80%
Minimum to qualify as well-capitalized balance $ 6,507.7 $ 6,165.3
Minimum to qualify as well-capitalized ratio 10.00% 10.00%
Leverage (Tier 1 Capital to Adjusted Average Fourth Quarter Assets)    
BALANCE $ 8,476.0 $ 8,722.5
RATIO 7.30% 7.30%
Minimum to qualify as well-capitalized balance $ 5,835.4 $ 5,998.6
Minimum to qualify as well-capitalized ratio 5.00% 5.00%
Supplementary Leverage Capital [Abstract]    
Supplementary leverage capital $ 8,476.0 $ 8,722.5
Supplementary leverage capital to average assets 6.40% 6.40%
Supplementary leverage capital required to be well capitalized $ 3,983.6 $ 4,077.2
Supplementary Leverage Ratio 3.00% 3.00%
ADVANCED APPROACH | The Northern Trust Company | Common Stock    
Tier 1 Capital    
BALANCE $ 8,476.0 $ 8,722.5
RATIO 13.00% 14.10%
Minimum to qualify as well-capitalized balance $ 4,230.0 $ 4,007.4
Minimum to qualify as well-capitalized ratio 6.50% 6.50%
ADVANCED APPROACH | The Northern Trust Company | Parent Company    
Tier 1 Capital    
BALANCE $ 8,898.7