"broad lines of" is correct and usable in written English.
You can use it to refer to something with many different details that can be broadly categorized. For example: "The report surveyed the broad lines of the local population's housing situation."
The broad lines of his life are well known.
And from that, the broad lines of their civilization can only be deduced.
In announcing his decision "to seek out new artistic challenges" next year, Mr. Noble said the broad lines of the company's renewal program were now in place.
The broad lines of contention had already been drawn in June during one of Belgium's most polarised general elections in years.
Responsible for the broad lines of policy, as well as for the system of terror that upheld the state, he left detailed administration to his subordinates.
The broad lines of the arguments are more or less predetermined by the subject: to what extent are state schools floundering; what subjects should be on the curriculum; are the middle classes hopelessly hypocritical about their own kids' education?
Ikon, which carries a broad line of products, or Hewlett, which makes computers, can more easily tout themselves as able to set up and manage full information structures.
There were few cars around to fill these avenues, but they provided a fine, broad line of sight for Soviet leaders during military parades.
Legal experts said the second guideline appeared to open a broad line of defense in at least some of the cases under review in the current scandal.
Because of H.P.'s broad line of PCs, printers and other consumer electronics, it also has considerable leverage over electronics retailers around the world for scarce shelf space.
"Accredited Home Lenders offers an unusually broad line of subprime mortgage products for wholesale mortgage brokers," the company's Web site boasted in its heyday.
