A surprisingly strong year in the financial markets made the richest members of Congress even wealthier in 2012, with the median net worth of the 50 richest rising more than 17 percent, CQ Roll Call’s annual survey of congressional wealth shows.

Lawmakers’ portfolios shrugged off pre-election jitters, concerns about the European debt crisis and suspense surrounding the fiscal cliff. It took a minimum reported net worth of $6.67 million just to crack the exclusive 50 Richest club.

Financial disclosures also revealed a widening gap between members’ wealth and that of their constituents. The median net worth of the 112th Congress stood at $442,007 in 2012. Nineteen percent of lawmakers reported no debts at all, while 15 percent had trusts.

In contrast, the median household net worth in the United States stood at $68,828 in 2011, with 69 percent of households holding some form of debt, according to the most recent U.S. Census statistics. Median household net worth decreased by 16 percent from 2000 to 2011, those figures show.

CQ Roll Call has reviewed the annual financial disclosure reports filed by all House and Senate lawmakers since 1990 to calculate the 50 richest members of Congress. Their minimum net worth is determined by subtracting the total minimum value of all liabilities from the total minimum value of all assets.

The disclosure forms reveal details such as each lawmaker’s stock market holdings, rental properties, checking accounts, credit card balances, student loans and other assets and liabilities.

Even so, the forms provide an incomplete and, in some cases, misleading picture of the overall wealth of lawmakers.

Assets and liabilities are listed in broad valuation categories spanning millions of dollars, making it impossible to determine a lawmaker’s precise net worth unless the individual opts to voluntarily disclose the actual dollar amounts. And though they’re required to report the value of mutual funds, stock holdings, bank accounts and other assets, they don’t have to disclose the value of personal residences or federal retirement savings accounts.

After years hovering near the top of the table, Rep. Darrell Issa, R-Calif., took the No. 1 spot on the 50 Richest list on the strength of holdings that swelled about $135 million in value. He supplanted Rep. Michael McCaul, R-Texas, who occupied the perch the previous two years and took an apparent “paper loss” by valuing several of his wife’s holdings, previously listed as worth at least $50 million, in the broad category of $1 million and above that’s reserved for spousal assets. Several longtime denizens of the 50 Richest fell off the list. Ex-Sen. John Kerry, D-Mass., left Congress for the State Department, while Sens. Herb Kohl, D-Wis., Olympia Snowe, R-Maine, and Ben Nelson, D-Neb., retired. Rep. Shelley Berkley, D-Nev., lost a Senate bid. And Sen. Frank R. Lautenberg, D-N.J., died in June.

A total of 37 of the 50 wealthiest members appeared on last year’s list. Eight others were freshmen.

Rep. John Delaney, D-Md., was the richest first-termer in the House, with a net worth of $68 million, primarily from his financial firm. Former Microsoft executive Suzan DelBene, D-Wash., was the richest woman in the freshman class, with a net worth of almost $24 million. Another noteworthy newcomer is Rep. Joseph P. Kennedy III, D-Mass., at No. 23, with almost all of his $15 million fortune connected to several family trusts.

Democratic Reps. Bill Foster of Illinois and Alan Grayson of Florida are back on the list after returning to Congress. Sen. Kay Hagan, D-N.C., rebounded after just failing to make the 50 Richest cut last year.

One of the biggest gainers in reported wealth last year was Louisiana Republican Rep. John Fleming, who climbed more than 50 spots to make the list for the first time in his congressional career. His Minden, La.-based real estate company, JCF Properties, increased in value from the $1 million to $5 million category to the $5 million to $25 million range.

More than a decade into his second stint in the House, Tennessee Democrat Jim Cooper doubled his net worth last year to $8 million. His share of the Cooper Brothers Land Partnership that owns farmland in Tennessee and Kentucky was worth $5.7 million. Last year, the same asset was listed in the $1 million to $5 million range.

An earlier version of the article misstated the location of JCF Properties.