Consolidated Balance Sheets In Millions, unless otherwise specified	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2011 Nominal Value in Dollars [Member] USD ($)	Dec. 31, 2010 Nominal Value in Dollars [Member] USD ($)	Dec. 31, 2011 Nominal Value in Euros [Member] EUR (€)	Dec. 31, 2010 Nominal Value in Euros [Member] EUR (€)
CURRENT ASSETS
Cash and cash equivalents	$ 436	$ 316
Accounts receivable, net	910	839
Fiduciary assets	9,338	9,569
Deferred tax assets	44	36
Other current assets	259	340
Total current assets	10,987	11,100
NON-CURRENT ASSETS
Fixed assets, net	406	381
Goodwill	3,295	3,294
Other intangible assets, net	420	492
Investments in associates	170	161
Deferred tax assets	22	7
Pension benefits asset	145	182
Other non-current assets	283	233
Total non-current assets	4,741	4,750
TOTAL ASSETS	15,728	15,850
CURRENT LIABILITIES
Fiduciary liabilities	9,338	9,569
Deferred revenue and accrued expenses	320	298
Income taxes payable	15	57
Short-term debt and current portion of long-term debt	15	110
Deferred tax liabilities	26	9
Other current liabilities	282	266
Total current liabilities	9,996	10,309
NON-CURRENT LIABILITIES
Long-term debt	2,354	2,157
Liability for pension benefits	270	167
Deferred tax liabilities	32	83
Provisions for liabilities	196	179
Other non-current liabilities	363	347
Total non-current liabilities	3,215	2,933
Total liabilities	13,211	13,242
COMMITMENTS AND CONTINGENCIES
EQUITY
Ordinary shares, $0.000115 nominal value; Authorized: 4,000,000,000; Issued 173,829,693 shares in 2011 and 170,883,865 shares in 2010 / Ordinary shares, EUR1 nominal value; Authorized: 40,000; Issued 40,000 shares in 2011 and 2010
Preference shares, $0.000115 nominal value; Authorized:1,000,000,000; Issued nil shares in 2011 and 2010
Additional paid-in capital	1,073	985
Retained earnings	2,160	2,136
Accumulated other comprehensive loss, net of tax	(744)	(541)
Treasury shares, at cost, 46,408 shares in 2011 and 2010 and 40,000 shares, EUR1 nominal value, in 2011 and 2010	(3)	(3)
Total Willis Group Holdings shareholders' equity	2,486	2,577
Noncontrolling interests	31	31
Total equity	2,517	2,608
TOTAL LIABILITIES AND EQUITY	$ 15,728	$ 15,850