REGULATORY MATTERS - Schedule of Capital Ratios (Detail) $ in Millions	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital, actual amount	$ 4,183	$ 3,531
Tier 1 capital, actual amount	3,511	2,984
Common equity tier 1, actual amount	3,405	2,877
Leverage, actual amount	3,511	2,984
Risk weighted assets, actual amount	$ 34,671	$ 28,991
Total capital, actual ratio	0.1206	0.1218
Total capital, tier 1 capital, actual ratio	0.1013	0.1029
Common equity tier 1, actual ratio	0.0982	0.0992
Leverage, actual ratio	0.0864	0.0799
Total capital, well-capitalized requirements amount	$ 3,467	$ 2,899
Tier 1 capital, well-capitalized requirements amount	$ 2,080	$ 1,739
Total capital, well-capitalized requirements ratio	0.1000	0.1000
Tier 1 capital, well-capitalized requirements ratio	0.0600	0.0600
Total capital, minimum capital requirements plus capital conservation buffer amount	$ 3,640	$ 3,044
Tier 1 capital, minimum capital requirements plus capital conservation buffer amount	2,947	2,464
Common equity tier 1, minimum capital requirements plus capital conservation buffer amount	2,427	2,029
Leverage, minimum capital requirements plus capital conservation buffer amount	$ 1,626	$ 1,493
Total capital, minimum capital requirements plus capital conservation buffer ratio	0.1050	0.1050
Tier 1 capital, minimum capital requirements plus capital conservation buffer ratio	0.0850	0.0850
Common equity tier 1, minimum capital requirements plus capital conservation buffer ratio	7.00%	7.00%
Leverage, minimum capital requirements plus capital conservation buffer ratio	0.0400	0.0400
FNBPA
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital, actual amount	$ 4,327	$ 3,695
Tier 1 capital, actual amount	3,640	3,098
Common equity tier 1, actual amount	3,560	3,018
Leverage, actual amount	3,640	3,098
Risk weighted assets, actual amount	$ 34,589	$ 28,930
Total capital, actual ratio	0.1251	0.1277
Total capital, tier 1 capital, actual ratio	0.1052	0.1071
Common equity tier 1, actual ratio	0.1029	0.1043
Leverage, actual ratio	0.0897	0.0831
Total capital, well-capitalized requirements amount	$ 3,459	$ 2,893
Tier 1 capital, well-capitalized requirements amount	2,767	2,314
Common equity tier 1, well-capitalized requirements amount	2,248	1,880
Leverage, well-capitalized requirements amount	$ 2,029	$ 1,864
Total capital, well-capitalized requirements ratio	0.1000	0.1000
Tier 1 capital, well-capitalized requirements ratio	0.0800	0.0800
Common equity tier 1, well-capitalized requirements ratio	6.50%	6.50%
Leverage, well-capitalized requirements ratio	0.0500	0.0500
Total capital, minimum capital requirements plus capital conservation buffer amount	$ 3,632	$ 3,038
Tier 1 capital, minimum capital requirements plus capital conservation buffer amount	2,940	2,459
Common equity tier 1, minimum capital requirements plus capital conservation buffer amount	2,421	2,025
Leverage, minimum capital requirements plus capital conservation buffer amount	$ 1,623	$ 1,491
Total capital, minimum capital requirements plus capital conservation buffer ratio	0.1050	0.1050
Tier 1 capital, minimum capital requirements plus capital conservation buffer ratio	0.0850	0.0850
Common equity tier 1, minimum capital requirements plus capital conservation buffer ratio	7.00%	7.00%
Leverage, minimum capital requirements plus capital conservation buffer ratio	0.0400	0.0400