According to the Random House Dictionary of Popular Proverbs and Sayings by Gregory Titelman, this phrase is a variation of "God is in the details".  The meaning being that details are important and that there may be "a catch hidden in the details".  The earliest attribution is anonymous, in the sixteenth edition of Bartlett's Familiar Quotations.  The saying is generally attributed to Gustave Flaubert (1821-80) who is quoted as saying, "Le bon Dieu est dans le detail" (God is in the details). Michelangelo, Mies van der Rohe and Warburg, an art historian, also lay claims to it.  See www.GoEnglish.com for common idiom listings.

The devil is in financial details too.  What makes a quirky little factoid, a factoid and what makes a factoid, significant, is a related subject.  When it comes to financial reporting, a little-known site, www.footnoted.org, publishing online since August 2003, takes a closer look at the things that companies "try to bury in their routine SEC filings".  Some of the little items that appear to be quirky and anecdotal are not really.  A trained mind of a financial auditor or analyst may uncover a serious issue of accounting, or something that tips off the trained student of financial reporting information as indicative of serious problems at a company.  Once again, the devil is in the details, or so it seems.

Financial sleuthing can be done on a global scale through a little-known European publisher, Bureau van Dijik Electronic Publishing. One of the most robust and extensive directory-databases that contain vast amounts of data on millions of public and private companies worldwide (some 35 million and counting in ORBIS alone)  Bureau van Dijik Electronic Publishing (BvDEP), headquartered in Brussels, Belgium, with offices throughout the world.   With names like AMADEUS, a pan-European database, ORBIS and extensive country-specific databases known as FAME, DIANE, DAFNE , BvD databases are ideal for in-depth research of individual companies, identifying companies complying with specific criteria plus detailed analysis of company peer groups and benchmarking.   Consider ORBIS.  It details extensive ownership data, shareholders, affiliates, as well as accounting data, financial information content, and more.  As you can expect, BvD is not  inexpensive. Deep pockets come in handy.  Is it any wonder Harvard University is a customer as is the US Dept. of Commerce?