Why is this IN-clause with subquery materialization slow?

Can someone help me explain why the performance of the two queries are so vastly different? (Setup-Code is at the end, DB-Fiddle is here: https://www.db-fiddle.com/f/eEuPWqR6gZcjbeSeWk4tu2/0)

1.

select id from texts WHERE id not in (select doc_id from details); 
select id from texts WHERE not exists (select 1 from details where details.doc_id=texts.id) 

When running the query select id from texts WHERE id not in (select doc_id from details); the query seems to run "forever". The query plan looks like this:

                                     QUERY PLAN                                      ------------------------------------------------------------------------------------  Gather  (cost=1000.00..3703524012.67 rows=400000 width=8)    Workers Planned: 2    ->  Parallel Seq Scan on texts  (cost=0.00..3703483012.67 rows=166667 width=8)          Filter: (NOT (SubPlan 1))          SubPlan 1            ->  Materialize  (cost=0.00..20220.86 rows=799991 width=8)                  ->  Seq Scan on details  (cost=0.00..13095.91 rows=799991 width=8)  JIT:    Functions: 8    Options: Inlining true, Optimization true, Expressions true, Deforming true (10 rows)  Time: 1.319 ms 

The costs already hint a much longer execution time, but I do not understand why the costs are that much bigger? Why does the Parallel Seq Scan on texts take so long? What is postgres doing here?

With fewer rows in the tables, I get the following query plan:

explain (analyse) select id from texts WHERE id not in (select doc_id from details);                                                                               QUERY PLAN                                                        -----------------------------------------------------------------------------------------------------------------------  Seq Scan on texts  (cost=11466.00..23744.18 rows=338247 width=8) (actual time=174.488..325.775 rows=10 loops=1)    Filter: (NOT (hashed SubPlan 1))    Rows Removed by Filter: 599990    SubPlan 1      ->  Seq Scan on details  (cost=0.00..9937.20 rows=611520 width=8) (actual time=0.014..56.549 rows=599990 loops=1)  Planning Time: 0.079 ms  Execution Time: 326.372 ms (7 rows) 

Why does it degrade that much with more rows? If I understand the output correctly the materialization itself is not the problem. Also how does the second query avoid this problem?

Schema/Data generation:

create table texts (   id bigint primary key,   url text);    create table details (   id bigserial primary key,   doc_id bigint,   content text);       insert into details (doc_id, content) select generate_series(1,800000), 'foobar'; insert into texts (id, url) select generate_series(1,800000), 'something';  # Delete some values delete from details where doc_id IN ( 307531, 630732, 86402, 584950, 835230, 334934, 673047, 772541, 239455, 763671);