Debt issued measured at amortized cost (Detail) - USD ($) $ in Millions		Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Disclosure Of Financial Liabilities [Line Items]
Certificates of deposit		$ 12,193	$ 14,723	$ 15,680
Commercial paper		25,304	26,591	25,472
Other short-term debt		5,219	6,080	5,515
Short-term debt	[1]	42,716	47,394	46,666
Senior unsecured debt that contributes to total loss-absorbing capacity (TLAC)		37,765	37,453	36,611
Senior unsecured debt other than TLAC		28,945	28,990	21,340
of which: issued by UBS AG with original maturity greater than one year	[2]	26,109	23,309	18,464
Covered bonds		1,449	2,606	2,796
Subordinated debt		20,072	19,327	22,157
of which: high-trigger loss-absorbing additional tier 1 capital instruments		12,330	11,573	11,837
of which: low-trigger loss-absorbing additional tier 1 capital instruments		2,509	2,501	2,577
of which: low-trigger loss-absorbing tier 2 capital instruments		4,686	4,709	7,201
of which: non-Basel III-compliant tier 2 capital instruments		547	544	543
Debt issued through the Swiss central mortgage institutions		8,963	8,911	9,660
Other long-term debt		0	2	3
Long-term debt	[3]	97,195	97,288	92,566
Total debt issued measured at amortized cost	[4]	$ 139,911	$ 144,682	$ 139,232
Unsecured portion of senior fixed-rate bonds issued by UBS AG with maturity greater than one year		100.00%	100.00%	100.00%

[1] <div>Debt with an original contractual maturity of less than one year</div>

[2] <div>Based on original contractual maturity without considering any early redemption features. As of 30 June 2021, 100% of the balance was unsecured (31 March 2021: 100%; 31 December 2020: 100%).</div>

[3] <div>Debt with an original contractual maturity greater than or equal to one year. The classification of debt issued into short-term and long-term does not consider any early redemption features.</div>

[4] <div>Net of bifurcated embedded derivatives, the fair value of which was not material for the periods presented.</div>