What you need to know on Wall Street today

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It's expected to be a noisy quarter for bank earnings in general, thanks in part to the tax law, which has caused many banks to book losses on repatriated cash and deferred tax assets that declined in value. Overall, Citi lost $18.3 billion, or $7.15 a share, for the quarter.

That included a one-time, non-cash charge of $22 billion, or $8.43 a share, on account of the new tax law.

Elsewhere in finance news, Goldman Sachs' vaunted commodities-trading team got butchered in 2017. Two of the biggest high-speed trading firms are joining forces in a deal that's a "sign of the times." And Apple, Amazon, and other tech titans could threaten big banks in one key area.

There's a ton of markets and investing news, so let's jump right in:

• Dow hits 26,000 for the first time
• CREDIT SUISSE: There are 3 things that could drive the stock market crazy in 2018
• There's a "significant risk to markets" that's a bigger worry than where the economy is headed next
• A dangerous trade that reminds experts of the 1987 market crash is riskier than ever
• David Einhorn's Greenlight Capital suffers, says "it feels like we have been running face first into the wind"
• Greenlight Capital is also betting that Twitter will have a winning year

In crypto news, two blockchain ETFs are launching - but the SEC asked them to take blockchain out of their names. Messaging app Telegram is looking to raise $1.2 billion in an ICO to become the Mastercard "for the new decentralized economy." The CEO of the oldest bitcoin exchange says all platforms are struggling with "the massive, massive amount of new users." And just about every cryptocurrency is getting smoked.