not worrying about or paying attention to possible problems
marked by blithe unconcern
Lachlain found it disturbing that they were all so insouciant about this. Here a Lykae lay with the youngest member of their household in his arms, in their home. In her bed.
He waited for them to realize this at any moment and attack.
Cole, Kresley (2006-03-28). A Hunger Like No Other (Immortals After Dark, Book 1) (Kindle Locations 5731-5733). Simon & Schuster, Inc.. Kindle Edition.
Definition from http://www.onelook.com/?w=insouciant&ls=a