Donald Trump’s presidential campaign has relied on insults and one-liners to catapult the billionaire to the top of the polls. Now, Trump is trying to add substance with the release of a policy paper on immigration.

In the paper, Trump calls for ending birthright citizenship, tripling of immigration officers and a wall between Mexico and the United States—paid for by the Mexican government.

“A lot of them come here, take the money, and go back into Mexico and the other countries because they still want to stay at their own country,” Trump said on Meet the Press Sunday. “You would be amazed. They want to stay in their own country. They have a loyalty to their own country.”

The details in the paper are among the most extensive offered on what has become Trump’s signature issue. For instance, Trump explains that he will force Mexico to pay for the wall with a variety of concrete threats like seizing funds sent into Mexico by illegal immigrants and increasing worker visa and border crossing fees

The paper was reportedly crafted with the help of Alabama GOP Senator Jeff Sessions. The two spoke by phone in July, according to the Washington Post. “I like him,” Trump told the Post. “Tough guy. I like that. We have a similar thought process.”

The immigration policy paper, rigidly conservative, focuses on the issue that catapulted Trump into the spotlight when he announced his presidential campaign. In late June, Trump attributed crime in the U.S. illegal immigration, at least in part.

“They’re sending people that have lots of problems, and they’re bringing those problems with us,” he said at the time. “They’re bringing drugs. They’re bringing crime. They’re rapists. And some, I assume, are good people.”

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Write to Justin Worland at justin.worland@time.com.