WASHINGTON (CNN) With Robert Mueller's investigation finished, Donald Trump's approval rating stands at its highest level since April 2017 in a new CNN Poll conducted by SSRS , as the share who say Democrats in Congress are doing too much to investigate the President rises 6 points.

Trump's approval rating remains largely negative in the new poll -- 52% disapprove and 43% approve -- but that approval figure is the highest -- by one point -- since a CNN poll completed around the 100-day mark of his time in office. At the same time, the share who say they strongly approve of the way the President is handling his job (35%) is at its highest level ever in CNN's polling.

The American public increasingly feels that Democrats in Congress are going too far in investigating the President -- 44% say Democrats are doing too much on that score, up from 38% saying so in March. That shift stems largely from independents, 46% of whom now say congressional Democrats are going too far.

Congressional Democrats have called for Attorney General William Barr to testify this week, including in front of the Senate Judiciary Committee on Wednesday, and have issued subpoenas to try to gain access to the full, unredacted version of Mueller's report and for former White House counsel Don McGahn to testify. The Treasury Department recently missed a deadline set by House Democrats for turning over the President's tax returns, and the Trump administration is fighting subpoenas issued for financial records from accounting firms and banks connected to Trump.

Even with growing concern about overreach, majorities want Congress to investigate whether Trump committed obstruction of justice in the course of the Mueller investigation (58%) and to pursue legal action to obtain the full, unredacted version of the Mueller report (61%). The public is divided on Barr's handling of the release of Mueller's report -- 44% approve and 43% disapprove, with a wide partisan gap.

About two-thirds still say Trump ought to release his tax returns (66%, including 52% who consider it important for the President to do). And most, 54%, say the President is not doing enough to cooperate with Democratic investigations.

The poll finds no change in the share of Americans who say they believe the President ought to be impeached compared with a March survey conducted before the completion of Mueller's investigation into Russian interference in the 2016 presidential election.

Overall, 37% say Trump should be impeached and removed from office, 59% say they do not feel that way. And while most who do back impeachment feel that way strongly (34% of adults strongly support impeachment, just 3% back it but not strongly), the share who strongly oppose it is larger (45% say they feel strongly that the President should not be impeached).

Trump's job approval rating has not risen significantly compared with last month's poll, but his standing now is a big improvement over where he stood in January amid a government shutdown. At the start of the year, just 37% of Americans approved of Trump's job performance, including only 36% of independents. Now, his 43% approval overall includes approval among nearly half of independents (46%), as well as 86% of Republicans and 5% Democrats.

Though his overall approval among Republicans hasn't moved much since the start of the year, Republican support has become stronger. In an early February poll, 65% of Republicans said they strongly approved of Trump's handling of the presidency. Now, 77% say the same. Those figures haven't moved as much among independents (33% now, 30% then) or Democrats (4% now, 1% then).

The positive signs for Trump in the poll may not be directly tied to Americans' impressions of how Trump fared in the Mueller report itself. About half (48%) say they believe Trump committed obstruction of justice during the course of Mueller's investigation, 45% say he did not. More still say that the things Trump has said publicly about the investigation have been mostly false (50%), than that they have been mostly true (43%). And 51% say they disapprove of the way the President handled the release of Mueller's report.

The end of Mueller's investigation has brought a boost in positive sentiment toward the special counsel. Nearly six in 10 (59%) say they approve of the way he handled the investigation, up from 48% before it was completed, and 48% say they have a favorable opinion of Mueller himself, up from 36% last fall.

The rise in Mueller's approval stems from a whopping 30-point increase in approval among Republicans (from 20% in March to 50% now) and a 12-point rise among independents (57%, up from 45%), while his numbers softened among Democrats (69% approve now, down from 75% in March). The increase in his favorability rating comes across party lines, though is largest among Republicans.

Public opinion on the investigation itself, however, has held about even with where it was before the release of a redacted version of Mueller's report earlier this month. About six in 10 (58%) say they think the investigation was a serious matter that deserved to be fully investigated, while 38% consider it mainly an effort to discredit Trump's presidency. Both figures moved little over the course of the investigation in CNN's polling.

In one point of partisan agreement over Mueller's work, 69% think Congress ought to investigate the origins of the Justice Department's inquiry into Russian interference in the 2016 election, including 76% of Democrats, 69% of independents and 62% of Republicans.

A scant 24% of Americans say they have read any of Mueller's report, 75% have opted not to dive in to the 448-page document, and just 3% report having read the whole thing.

The CNN Poll was conducted by SSRS April 25 through 28 among a random national sample of 1,007 adults reached on landlines or cellphones by a live interviewer. Results for the full sample have a margin of sampling error of plus or minus 3.8 percentage points.