( We've all heard about those cushy perks that go with being a member of Congress, not the least of which are heavily subsidized health benefits.

But how much of this taxpayer-supported largesse - aside from his annual $174,000 salary - will go toward the likely $658 daily bill Rep. Trey Radel, R-Fort Myers, is racking up at a Naples addiction treatment center? In short, no one but Radel can say for sure.

Radel enrolled in an inpatient program at Hazelden on Nov. 21, a day after pleading guilty to a misdemeanor-level cocaine possession charge in Washington. He blamed his alcoholism for the illegal drug use.

His office confirmed that the congressman uses federal health insurance benefits, though it would not specify the policy he holds. Radel's representatives also could not say if he is using the insurance to help pay for his substance abuse treatment in Naples.

The federal Office of Personnel Management, which oversees government benefits, offers this general rule in an alcohol abuse handbook for supervisors:

"The cost of treatment is the employee's responsibility. All Federal Employee Health Benefit Plans have some kind of coverage; however, that coverage is limited."

Despite repeated attempts, the OPM media office refused to speak to me on the phone about this issue last week, citing Thanksgiving week scheduling conflicts.

OPM spokesman Edmund Byrnes did send me this general statement, which reads in part: "Plans ... have a wide variety of benefit structures, including various provisions of in and out of network providers, and varying co-pays and co-insurance levels that apply to regular care as well as mental health and substance abuse treatment."

The federal health insurance program covers about 8 million federal workers, according to a 2012 government report to Congress. The number of current and former members of Congress using the plan was not included in that report, however.

The government pays much of the premium costs, similar to cost-sharing arrangements for those getting insurance in the private sector. The government's share may not exceed 75 percent of any plan's premium. That means, on average, the government pays $178.83 for an individual employee's bi-weekly cost, according to that government report. Individuals are responsible for an average $78.95.

Benefits for federal employees like Radel generally do cover mental health care, as noted before. In January, they will switch over to the insurance buying exchanges created by the Affordable Care Act. The new Obamacare-regulated plans must offer some mental health and substance abuse coverage, a fact some of the law's critics have argued will lead to unnecessary premium increases.