Jack Nicholson . . . turned to an assistant, bummed a cigarette, flashed one of his wolfish, insouciant grins and said, We all have our little secrets, Seany..
An insouciant action or quality shows someone's lack of concern about something which they might be expected to take more seriously. Programme-makers seem irresponsibly insouciant about churning out violence. = nonchalant
marked by blithe unconcern; "an ability to interest casual students"; "showed a casual disregard for cold weather"; "an utterly insouciant financial policy"; "an elegantly insouciant manner"; "drove his car with nonchalant abandon"; "was polite in a teasing nonchalant manner"