SQL tree duplication

Hi,

I have the following kind of sql structure, in 3 levels:

-----------------------
create table documents (
id serial,
name varchar(50),
primary key (id)
);

create table lines (
id serial,
name varchar(50),
document_id integer,
primary key (id),
foreign key (document_id) references documents (id)
);

create table line_details (
id serial,
name varchar(50),
line_id integer,
primary key (id),
foreign key (line_id) references lines (id)
);
-----------------------

I'd like to be able to "duplicate" a document, with all of its lines and
line details.

Is there any easy way to do that with Postgresql? The only solution I
can think of at the moment is to loop through all lines and line
details, and replace foreign keys properly with values fetch with
"currval". It should work just fine, but I was wondering if some
advanced features of Postgresql could help in this situation.

Regards,

Philippe Lang