Arthur J. Gallagher & Co. (AJG) 10-Q 30 Oct 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	30-Sep-13
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3
Trading Symbol	AJG
Entity Registrant Name	GALLAGHER ARTHUR J & CO
Entity Central Index Key	354190
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	131,538,000

Consolidated_Statement_of_Earn

Consolidated Statement of Earnings (USD $)	3 Months Ended		9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement [Abstract]
Commissions	$399.10	$346	$1,126.80	$962.70
Fees	270	248.2	778.6	706
Supplemental commissions	17.8	16.6	53.4	50.3
Contingent commissions	6.5	7.7	43.5	37
Investment income	2.6	2.7	5.5	8
Net gains on books of business sales		0.7	3.3	1.4
Revenues from clean coal activities	134.9	28.4	264.1	80.3
Other net revenues	4.9	0.1	14.2	1.4
Total revenues	835.8	650.4	2,289.40	1,847.10
Compensation	412.5	373.9	1,211.90	1,082.40
Operating	133.1	121.6	404.7	353.6
Cost of revenues from clean coal activities	146.9	27.7	281.6	74.4
Interest	13.1	10.7	36.2	32.1
Depreciation	14.3	10.7	38.2	30.6
Amortization	30.8	25.8	90.1	73.1
Change in estimated acquisition earnout payables	-0.4	3.7	1.5	1
Total expenses	750.3	574.1	2,064.20	1,647.20
Earnings before income taxes	85.5	76.3	225.2	199.9
Provision for income taxes	10.9	14.6	16.6	38.4
Net earnings	$74.60	$61.70	$208.60	$161.50
Basic net earnings per share	$0.57	$0.50	$1.63	$1.35
Diluted net earnings per share	$0.57	$0.50	$1.61	$1.33
Dividends declared per common share	$0.35	$0.34	$1.05	$1.02

Consolidated_Statement_of_Comp

Consolidated Statement of Comprehensive Earnings (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net earnings	$74.60	$61.70	$208.60	$161.50
Change in pension liability, net of taxes	0.2	1	0.4	2
Foreign currency translation	29.1	19.6	-9.9	17.4
Change in fair value of derivative investments, net of taxes	1.5	1.7	0.5	2
Comprehensive earnings	$105.40	$84	$199.60	$182.90

Consolidated_Balance_Sheet

Consolidated Balance Sheet (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Statement Of Financial Position [Abstract]
Cash and cash equivalents	$286.90	$302.10
Restricted cash	924.2	851.6
Premiums and fees receivable	1,075.10	1,096.10
Other current assets	260.5	179.7
Total current assets	2,546.70	2,429.50
Fixed assets-net	148.1	105.4
Deferred income taxes	283.6	251.8
Other noncurrent assets	302.3	283.3
Goodwill-net	1,771.50	1,472.70
Amortizable intangible assets-net	918	809.6
Total assets	5,970.20	5,352.30
Premiums payable to insurance and reinsurance companies	1,875.90	1,819.70
Accrued compensation and other accrued liabilities	361.3	306.7
Unearned fees	69.7	70.6
Other current liabilities	35.5	36.9
Corporate related borrowings-current	235.5	129
Total current liabilities	2,577.90	2,362.90
Corporate related borrowings-noncurrent	825	725
Other noncurrent liabilities	635.1	605.8
Total liabilities	4,038	3,693.70
Stockholders' equity:
Common stock-issued and outstanding 131.5 shares in 2013 and 125.6 shares in 2012	131.5	125.6
Capital in excess of par value	1,259.30	1,055.40
Retained earnings	583.2	510.4
Accumulated other comprehensive loss	-41.8	-32.8
Total stockholders' equity	1,932.20	1,658.60
Total liabilities and stockholders' equity	$5,970.20	$5,352.30

Consolidated_Balance_Sheet_Par

Consolidated Balance Sheet (Parenthetical)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Statement Of Financial Position [Abstract]
Common stock - issued shares	131.5	125.6
Common stock - outstanding shares	131.5	125.6

Consolidated_Statement_of_Cash

Consolidated Statement of Cash Flows (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net earnings	$208.60	$161.50
Adjustments to reconcile net earnings to net cash provided by operating activities:
Net gain on investments and other	-17.6	-1.4
Depreciation and amortization	128.3	103.7
Change in estimated acquisition earnout payables	1.5	1
Amortization of deferred compensation and restricted stock	10.6	6.4
Stock-based and other noncash compensation expense	5.4	5.5
Effect of changes in foreign exchange rates		0.9
Net change in restricted cash	-29.3	-65.7
Net change in premiums receivable	62.3	75.1
Net change in premiums payable	-7.2	-55.5
Net change in other current assets	-71.5	12.2
Net change in accrued compensation and other accrued liabilities	50.1	-42.6
Net change in fees receivable/unearned fees	-11.3	-7.9
Net change in income taxes payable	9.5	12.9
Net change in deferred income taxes	-36.6	3.3
Net change in other noncurrent assets and liabilities	-24.2	-30
Net cash provided by operating activities	278.6	179.4
Cash flows from investing activities:
Net additions to fixed assets	-69.8	-36.1
Cash paid for acquisitions, net of cash acquired	-333	-137.9
Net proceeds from sales of operations/books of business	3.3	8.9
Net (funding) proceeds of investment transactions	-31	10.7
Net cash used by investing activities	-430.5	-154.4
Cash flows from financing activities:
Proceeds from issuance of common stock	64.5	60.9
Tax impact from issuance of common stock	6.3	3.7
Dividends paid	-136	-119.7
Borrowings on line of credit facility	445.5	162
Repayments on line of credit facility	-439	-172
Borrowings of corporate related long-term debt	200	50
Net cash provided (used) by financing activities	141.3	-15.1
Effect of changes in foreign exchange rates on cash and cash equivalents	-4.6	4.1
Net (decrease) increase in cash and cash equivalents	-15.2	14
Cash and cash equivalents at beginning of period	302.1	291.2
Cash and cash equivalents at end of period	286.9	305.2
Supplemental disclosures of cash flow information:
Interest paid	40.4	38
Income taxes paid	$37.10	$24.50

Consolidated_Statement_of_Stoc

Consolidated Statement of Stockholders' Equity (USD $)	Total	Common Stock [Member]	Capital in Excess of Par Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
In Millions, unless otherwise specified
Balance at Dec. 31, 2012	$1,658.60	$125.60	$1,055.40	$510.40	($32.80)
Beginning, Shares at Dec. 31, 2012		125.6
Net earnings	208.6			208.6
Change in pension liability, net of taxes of $0.2 million	0.4				0.4
Foreign currency translation	-9.9				-9.9
Change in fair value of derivative instruments, net of taxes of $0.3 million	0.5				0.5
Compensation expense related to stock option plan grants	5.4		5.4
Tax impact from issuance of common stock	6.3		6.3
Common stock issued in:
Four purchase transactions	151.2	3.4	147.8
Four purchase transactions (in shares)		3.4
Stock option plans	56.5	2.1	54.4
Stock option plans (in shares)	2.1	2.1
Employee stock purchase plan	8	0.2	7.8
Employee stock purchase plan (in shares)		0.2
Deferred compensation and restricted stock	-17.6	0.2	-17.8
Deferred compensation and restricted stock (in shares)		0.2
Cash dividends declared on common stock	-135.8			-135.8
Balance at Sep. 30, 2013	$1,932.20	$131.50	$1,259.30	$583.20	($41.80)
Balance, Shares at Sep. 30, 2013		131.5

Consolidated_Statement_of_Stoc1

Consolidated Statement of Stockholders' Equity (Parenthetical) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Statement Of Stockholders Equity [Abstract]
Tax effect on net change in pension liability	$0.20
Net change in fair value of derivative instruments, tax	$0.30

Nature_of_Operations_and_Basis

Nature of Operations and Basis of Presentation	9 Months Ended
	Sep. 30, 2013
Accounting Policies [Abstract]
Nature of Operations and Basis of Presentation	1. Nature of Operations and Basis of Presentation
	Arthur J. Gallagher & Co. and its subsidiaries, collectively referred to herein as we, our, us or the company, provide insurance brokerage and risk management services to a wide variety of commercial, industrial, institutional and governmental organizations through three reportable segments. Commission and fee revenue generated by the brokerage segment is primarily related to the negotiation and placement of insurance for our clients. Fee revenue generated by the risk management segment is primarily related to claims management, information management, risk control consulting (loss control) services and appraisals in the property/casualty market. Investment income and other revenue are generated from our investment portfolio, which includes invested cash and restricted funds, as well as clean energy and other investments. We are headquartered in Itasca, Illinois, have operations in 20 countries and offer client-service capabilities in more than 140 countries globally through a network of correspondent insurance brokers and consultants.
	We have prepared the accompanying unaudited consolidated financial statements pursuant to the rules and regulations of the Securities and Exchange Commission. Certain information and footnote disclosures normally included in annual financial statements have been omitted pursuant to such rules and regulations. We believe the disclosures are adequate to make the information presented not misleading. The unaudited consolidated financial statements included herein are, in the opinion of management, prepared on a basis consistent with our audited consolidated financial statements for the year ended December 31, 2012 and include all normal recurring adjustments necessary for a fair presentation of the information set forth. The quarterly results of operations are not necessarily indicative of the results of operations to be reported for subsequent quarters or the full year. These unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2012.
	Certain reclassifications have been made to the amounts reported in the prior year’s unaudited consolidated financial statements in order to conform to the current year presentation.
	In the preparation of our unaudited consolidated financial statements as of September 30, 2013, management evaluated all material subsequent events or transactions that occurred after the balance sheet date through the date on which the financial statements were issued, for potential recognition or disclosure therein.

Effect_of_New_Accounting_Prono

Effect of New Accounting Pronouncements	9 Months Ended
	Sep. 30, 2013
Accounting Changes And Error Corrections [Abstract]
Effect of New Accounting Pronouncements	2. Effect of New Accounting Pronouncements
	Presentation of Unrecognized Tax Benefits
	In July 2013, the Financial Accounting Standards Board (which we refer to as the FASB) issued ASU 2013-11, “Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists,” which provides explicit guidance on the presentation of certain unrecognized tax benefits in the financial statements that did not previously exist. The ASU provides that a liability related to an unrecognized tax benefit would be offset against a deferred tax asset for a net operating loss carryforward, a similar tax loss or a tax credit carryforward if such settlement is required or expected in the event the uncertain tax position is disallowed. In that case, the liability associated with the unrecognized tax benefit is presented in the financial statements as a reduction to the related deferred tax asset. In situations in which a net operating loss carryforward, a similar tax loss or a tax credit carryforward is not available at the reporting date under the tax law of the jurisdiction or the tax law of the jurisdiction does not require, and the entity does not intend to use, the deferred tax asset for such purpose, the unrecognized tax benefit will be presented in the financial statements as a liability and will not be combined with deferred tax assets. This new guidance is effective for annual and interim periods beginning after December 15, 2013. Early adoption is permitted. Management is currently evaluating whether or not to early adopt and the impact of the new guidance upon adoption, but believes that the impact on the financial statements will not be material.
	Other Comprehensive Income
	In February 2013, the FASB issued ASU 2013-02, Comprehensive Income (Topic 220), “Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income,” which requires significant items reclassified out of accumulated other comprehensive income (which we refer to as AOCI) to net income in their entirety in the same reporting period, to be reported to show the effect of the reclassifications on the respective line items of the statement where net income is presented. These reclassifications can be presented either on the face of the statement where net income is presented or in the notes to the financial statements. For items that are not reclassified to net income in their entirety in the same reporting period, a cross reference to other disclosures currently required under U.S. GAAP is required in the notes to the consolidated financial statements. The new guidance also requires companies to report changes in the accumulated balances of each component of AOCI. This new guidance was effective for annual and interim periods beginning after December 15, 2012. We adopted the new guidance effective January 1, 2013. The adoption affected the disclosures made in our unaudited consolidated financial statements and notes thereto, but did not have any impact on our results of operations or financial position.

Business_Combinations

Business Combinations	9 Months Ended
	Sep. 30, 2013
Business Combinations [Abstract]
Business Combinations	3. Business Combinations
	During the nine-month period ended September 30, 2013, we acquired substantially all of the net assets of the following firms in exchange for our common stock and/or cash. These acquisitions have been accounted for using the acquisition method for recording business combinations (in millions except share data):
	Name and Effective	Common		Common		Cash		Accrued		Escrow		Recorded		Total		Maximum
	Date of Acquisition	Shares		Share		Paid		Liability		Deposited		Earnout		Recorded		Potential
		Issued		Value								Payable		Purchase		Earnout
														Price		Payable
		(000s)
	Metzler Brothers Insurance February 1, 2013		—	$	—	$	3.4	$	—	$	0.4	$	0.7	$	4.5	$	1.4
	Advanced Benefit Advisors, Inc. (ABA) April 1, 2013		—		—		10.9		—		0.1		1.8		12.8		7
	Property & Commercial Limited (PCL) April 1, 2013		—		—		65.1		—		—		—		65.1		—
	Garza Long Group, LLC (GLG) May 1, 2013		—		—		4.3		—		0.1		0.5		4.9		6.7
	Bollinger, Inc. (BOL) August 1, 2013		3,177		140		155.1		—		22		—		317.1		—
	Dickinson & Associates, Inc. (DA) August 1, 2013		—		—		10.9		—		0.1		0.5		11.5		4.8
	Belmont International (BEL) September 1, 2013		—		—		21.7		—		2.5		2.8		27		3.2
	R.W. Scobie, Inc. (RWS) September 1, 2013		223		9.5		4.4		—		—		2.4		16.3		5
	Jeffrey Haber & Michael Fischman (HF) September 20, 2013		—		—		7		—		—		8.4		15.4		10.3
	Eight other acquisitions completed in 2013		30		1.4		8.4		—		0.4		6.4		16.6		8.7
			3,430	$	150.9	$	291.2	$	—	$	25.6	$	23.5	$	491.2	$	47.1
	On September 4, 2013 we signed an agreement to acquire the Giles Group of Companies (which we refer to as Giles) headquartered in London, England. Under the agreement, we agreed to purchase all of the outstanding shares of Giles for net cash consideration of approximately £233 million, or approximately $370 million. The transaction is subject to regulatory approval and is expected to close in early November 2013. Giles is the fifth largest independent retail insurance broker in the United Kingdom with over 1,100 employees operating out of 43 offices in England, Scotland, Wales, Northern Ireland, Isle of Man and the Channel Islands. In the nine-month period ended September 30, 2013, we recognized an unrealized fair value pretax gain of $5.0 million related to three foreign currency derivative investment contracts that we executed in September 2013 in connection with the signing of the agreement to acquire Giles. This unrealized gain was included in other net revenues in the consolidated statement of earnings. The derivative investment contracts will expire by October 31, 2013.
	Common shares issued in connection with acquisitions are valued at closing market prices as of the effective date of the applicable acquisition. We record escrow deposits that are returned to us as a result of adjustments to net assets acquired as reductions of goodwill when the escrows are settled. The maximum potential earnout payables disclosed in the foregoing table represent the maximum amount of additional consideration that could be paid pursuant to the terms of the purchase agreement for the applicable acquisition. The amounts recorded as earnout payables, which are primarily based upon the estimated future operating results of the acquired entities over a two- to three-year period subsequent to the acquisition date, are measured at fair value as of the acquisition date and are included on that basis in the recorded purchase price consideration for the applicable acquisition. We will record subsequent changes in these estimated earnout obligations, including the accretion of discount, in our consolidated statement of earnings when incurred.
	The fair value of these earnout obligations is based on the present value of the expected future payments to be made to the sellers of the acquired entities in accordance with the provisions outlined in the respective purchase agreements. In determining fair value, we estimated the acquired entity’s future performance using financial projections developed by management for the acquired entity and market participant assumptions that were derived for revenue growth and/or profitability. Revenue growth rates generally ranged from 2.0% to 10.0% for our 2013 acquisitions. We estimated future payments using the earnout formula and performance targets specified in each purchase agreement and these financial projections. We then discounted these payments to present value using a risk-adjusted rate that takes into consideration market-based rates of return that reflect the ability of the acquired entity to achieve the targets. These discount rates generally ranged from 8.0% to 8.5% for all of our 2013 acquisitions. Changes in financial projections, market participant assumptions for revenue growth and/or profitability, or the risk-adjusted discount rate, would result in a change in the fair value of recorded earnout obligations.
	During each of the three-month periods ended September 30, 2013 and 2012, we recognized $2.9 million and $2.4 million, respectively, of expense in our consolidated statement of earnings related to the accretion of the discount recorded for earnout obligations in connection with our acquisitions. During each of the nine-month periods ended September 30, 2013 and 2012, we recognized $8.7 million and $7.0 million, respectively, of expense in our consolidated statement of earnings related to the accretion of the discount recorded for earnout obligations in connection with our acquisitions. In addition, during the three-month periods ended September 30, 2013 and 2012, we recognized $3.3 million of income and $1.3 million of expense, respectively, related to net adjustments in the estimated fair value of earnout obligations in connection with revised projections of future performance for twenty and twelve acquisitions, respectively. In addition, during the nine-month periods ended September 30, 2013 and 2012, we recognized $7.2 million and $6.0 million of income, respectively, related to net adjustments in the estimated fair value of earnout obligations in connection with revised projections of future performance for fifty-three and thirty-one acquisitions, respectively. The aggregate amount of maximum earnout obligations related to acquisitions made in 2009 and subsequent years was $400.4 million as of September 30, 2013, of which $140.4 million was recorded in our consolidated balance sheet as of September 30, 2013, based on the estimated fair value of the expected future payments to be made.
	The following is a summary of the estimated fair values of the net assets acquired at the date of each acquisition made in the nine-month period ended September 30, 2013 (in millions):
		ABA		PCL		GLG		BOL		DA		BEL		RWS		HF		Nine		Total
																		Other
																		Acquisitions
	Cash	$	—	$	2.4	$	—	$	7.6	$	0.6	$	5.3	$	0.2	$	—	$	0.2	$	16.3
	Other current assets		—		32.9		—		39.4		—		19.1		8.2		—		0.2		99.8
	Fixed assets		—		2.7		—		3.1		—		0.4		0.4		—		0.2		6.8
	Noncurrent assets		—		0.4		—		2.2		—		—		—		—		—		2.6
	Goodwill		7.6		44.6		2.4		197		4		15.3		12.8		8.4		7.9		300
	Expiration lists		5		25.6		2.4		132.5		7.3		9		6.7		6.7		13.4		208.6
	Non-compete agreements		0.2		—		0.1		0.4		0.2		0.2		—		0.3		0.4		1.8
	Trade names		—		0.1		—		1.7		—		—		—		—		—		1.8
	Total assets acquired		12.8		108.7		4.9		383.9		12.1		49.3		28.3		15.4		22.3		637.7
	Current liabilities		—		35.5		—		50.9		0.6		20.5		9.4		—		0.7		117.6
	Noncurrent liabilities		—		8.1		—		15.9		—		1.8		2.6		—		0.5		28.9
	Total liabilities assumed		—		43.6		—		66.8		0.6		22.3		12		—		1.2		146.5
	Total net assets acquired	$	12.8	$	65.1	$	4.9	$	317.1	$	11.5	$	27	$	16.3	$	15.4	$	21.1	$	491.2
	Among other things, these acquisitions allow us to expand into desirable geographic locations, further extend our presence in the retail and wholesale insurance brokerage services and risk management industries and/or increase the volume of general services currently provided. The excess of the purchase price over the estimated fair value of the tangible net assets acquired at the acquisition date was allocated to goodwill, expiration lists, non-compete agreements and trade names in the amounts of $300.0 million, $208.6 million, $1.8 million and $1.8 million, respectively, within the brokerage segment.
	Provisional estimates of fair value are established at the time of the acquisition and are subsequently reviewed within the first year of operations subsequent to the acquisition date to determine the necessity for adjustments. The fair value of the tangible assets and liabilities for each applicable acquisition at the acquisition date approximated their carrying values. The fair value of expiration lists was established using the excess earnings method, which is an income approach based on estimated financial projections developed by management for each acquired entity using market participant assumptions. Revenue growth and attrition rates generally ranged from 2.0% to 10.0% and 5.0% to 15.0%, respectively, for our 2012 and 2013 acquisitions, for which a valuation was performed in the nine-month period ended September 30, 2013. We estimate the fair value as the present value of the benefits anticipated from ownership of the subject customer list in excess of returns required on the investment in contributory assets necessary to realize those benefits. The rate used to discount the net benefits was based on a risk-adjusted rate that takes into consideration market-based rates of return and reflects the risk of the asset relative to the acquired business. These discount rates generally ranged from 10.5% to 14.0% for our 2012 and 2013 acquisitions, for which a valuation was performed in the nine-month period ended September 30, 2013. The fair value of non-compete agreements was established using the profit differential method, which is an income approach based on estimated financial projections developed by management for the acquired company using market participant assumptions and various non-compete scenarios.
	Expiration lists, non-compete agreements and trade names related to our acquisitions are amortized using the straight-line method over their estimated useful lives (three to fifteen years for expiration lists, three to five years for non-compete agreements and five to ten years for trade names), while goodwill is not subject to amortization. We use the straight-line method to amortize these intangible assets because the pattern of their economic benefits cannot be reasonably determined with any certainty. We review all of our intangible assets for impairment periodically (at least annually) and whenever events or changes in business circumstances indicate that the carrying value of the assets may not be recoverable. In reviewing intangible assets, if the fair value is less than the carrying amount of the respective (or underlying) asset, an indicator of impairment would exist and further analysis would be required to determine whether or not a loss would need to be charged against current period earnings. Based on the results of impairment reviews during the nine-month period ended September 30, 2013, we wrote off $2.2 million of amortizable intangible assets related to the brokerage segment. Based on the results of impairment reviews during the three-month and nine-month periods ended September 30, 2012, we wrote off $0.3 million and $3.4 million, respectively, of amortizable intangible assets related to the brokerage segment.
	Of the $208.6 million of expiration lists, $1.8 million of non-compete agreements and $1.8 million of trade names related to our acquisitions made during the nine-month period ended September 30, 2013, $174.9 million, $0.7 million and $1.8 million, respectively, is not expected to be deductible for income tax purposes. Accordingly, we recorded a deferred tax liability of $23.4 million, and a corresponding amount of goodwill, in the nine-month period ended September 30, 2013 related to nondeductible amortizable intangible assets.
	During the nine-month period ended September 30, 2012, we issued 425,000 shares of our common stock and paid $3.4 million in cash related to earnout obligations of four acquisitions made prior to 2009 and recorded additional goodwill of $0.1 million.
	Our consolidated financial statements for the nine-month period ended September 30, 2013 include the operations of the acquired entities from their respective acquisition dates. The following is a summary of the unaudited pro forma historical results, as if these entities had been acquired at January 1, 2012 (in millions, except per share data):
		Three-month period ended				Nine-month period ended
		September 30,				September 30,
		2013		2012		2013		2012
	Total revenues	$	850.9	$	693.7	$	2,385.90	$	1,981.00
	Net earnings		75.2		63.5		216.2		168.7
	Basic net earnings per share		0.57		0.5		1.66		1.37
	Diluted net earnings per share		0.57		0.5		1.64		1.35
	The unaudited pro forma results above have been prepared for comparative purposes only and do not purport to be indicative of the results of operations which actually would have resulted had these acquisitions occurred at January 1, 2012, nor are they necessarily indicative of future operating results. Annualized revenues of the businesses acquired during the nine-month period ended September 30, 2013 totaled approximately $176.4 million. For the nine-month period ended September 30, 2013, total revenues and net earnings recorded in our unaudited consolidated statement of earnings related to our acquisitions made during the nine-month period ended September 30, 2013 in the aggregate, were $41.5 million and $4.3 million, respectively.

Intangible_Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2013
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible Assets	4. Intangible Assets
	The carrying amount of goodwill at September 30, 2013 and December 31, 2012 allocated by domestic and foreign operations is as follows (in millions):
		Brokerage			Risk			Corporate		Total
					Management
	At September 30, 2013
	United States	$	1,398.60		$	19.3		$	—	$	1,417.90
	Foreign, principally Australia, Canada and the U.K.		351.6			2			—		353.6
	Total goodwill - net	$	1,750.20		$	21.3		$	—	$	1,771.50
	At December 31, 2012
	United States	$	1,158.10		$	19.2		$	—	$	1,177.30
	Foreign, principally Australia, Canada and the U.K.		293.3			2.1			—		295.4
	Total goodwill - net	$	1,451.40		$	21.3		$	—	$	1,472.70
	The changes in the carrying amount of goodwill for the nine-month period ended September 30, 2013 are as follows (in millions):
					Risk
		Brokerage			Management			Corporate		Total
	Balance as of December 31, 2012	$	1,451.40		$	21.3		$	—	$	1,472.70
	Goodwill acquired during the period		300			—			—		300
	Goodwill adjustments due to appraisals and other acquisition adjustments		3.3			—			—		3.3
	Foreign currency translation adjustments during the period		(4.5	)		—			—		(4.5	)
	Balance as of September 30, 2013	$	1,750.20		$	21.3		$	—	$	1,771.50
	Major classes of amortizable intangible assets at September 30, 2013 and December 31, 2012 consist of the following (in millions):
		September 30,			December 31,
		2013			2012
	Expiration lists	$	1,372.40		$	1,175.00
	Accumulated amortization - expiration lists		(477.1	)		(390.8	)
			895.3			784.2
	Non-compete agreements		31.8			30.9
	Accumulated amortization - non-compete agreements		(25.0	)		(23.3	)
			6.8			7.6
	Trade names		22.4			23
	Accumulated amortization - trade names		(6.5	)		(5.2	)
			15.9			17.8
	Net amortizable assets	$	918		$	809.6
	Estimated aggregate amortization expense for each of the next five years is as follows:
	2013 (remaining three months)	$	32.6
	2014		128.5
	2015		123.4
	2016		117.9
	2017		109.8
	Total	$	512.2

Credit_and_Other_Debt_Agreemen

Credit and Other Debt Agreements	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]
Credit and Other Debt Agreements	5. Credit and Other Debt Agreements
	Note Purchase Agreement - We are a party to an amended and restated note purchase agreement dated December 19, 2007, with certain accredited institutional investors, pursuant to which we issued and sold $100.0 million in aggregate principal amount of our 6.26% Senior Notes, Series A, due August 3, 2014 and $300.0 million in aggregate principal amount of our 6.44% Senior Notes, Series B, due August 3, 2017, in a private placement. These notes require semi-annual payments of interest that are due in February and August of each year.
	We are a party to a note purchase agreement dated November 30, 2009, with certain accredited institutional investors, pursuant to which we issued and sold $150.0 million in aggregate principal amount of our 5.85% Senior Notes, Series C, due in three equal installments on November 30, 2016, November 30, 2018 and November 30, 2019, in a private placement. These notes require semi-annual payments of interest that are due in May and November of each year.
	We are a party to a note purchase agreement dated February 10, 2011, with certain accredited institutional investors, pursuant to which we issued and sold $75.0 million in aggregate principal amount of our 5.18% Senior Notes, Series D, due February 10, 2021 and $50.0 million in aggregate principal amount of our 5.49% Senior Notes, Series E, due February 10, 2023, in a private placement. These notes require semi-annual payments of interest that are due in February and August of each year.
	We are a party to a note purchase agreement dated July 10, 2012, with certain accredited institutional investors, pursuant to which we issued and sold $50.0 million in aggregate principal amount of our 3.99% Senior Notes, Series F, due July 10, 2020, in a private placement. These notes require semi-annual payments of interest that are due in January and July of each year.
	We are a party to a note purchase agreement dated June 14, 2013, with certain accredited institutional investors, pursuant to which we issued and sold $200.0 million in aggregate principal amount of our 3.69% Senior Notes, Series G, due June 14, 2022, in a private placement. These notes require semi-annual payments of interest that are due in June and December of each year.
	Under the terms of the note purchase agreements, we may redeem the notes at any time, in whole or in part, at 100% of the principal amount of such notes being redeemed, together with accrued and unpaid interest and a “make-whole amount.” The “make-whole amount” is derived from a net present value computation of the remaining scheduled payments of principal and interest using a discount rate based on U.S. Treasury yields plus 0.5% and is designed to compensate the purchasers of the notes for their investment risk in the event prevailing interest rates at the time of prepayment are less favorable than the interest rates under the notes. We do not currently intend to prepay any of the notes.
	The note purchase agreements contain customary provisions for transactions of this type, including representations and warranties regarding us and our subsidiaries and various financial covenants, including covenants that require us to maintain specified financial ratios. We were in compliance with these covenants as of September 30, 2013. The note purchase agreements also provide customary events of default, generally with corresponding grace periods, including, without limitation, payment defaults with respect to the notes, covenant defaults, cross-defaults to other agreements evidencing our or our subsidiaries’ indebtedness, certain judgments against us or our subsidiaries and events of bankruptcy involving us or our material subsidiaries.
	The notes issued under the note purchase agreements are senior unsecured obligations of ours and rank equal in right of payment with our Credit Agreement discussed below.
	Credit Agreement - On September 19, 2013, we entered into a $600.0 million unsecured multicurrency credit agreement (which we refer to as the Credit Agreement), which expires on September 19, 2018, with a group of fifteen financial institutions. The Credit Agreement replaced a $500.0 million unsecured revolving credit facility (that was scheduled to expire on July 14, 2014), which was terminated upon the execution of the Credit Agreement. All indebtedness, liabilities and obligations outstanding under the previous facility were fully paid and satisfied, except for the letters of credit (which we refer to as LOCs) which became LOCs under the Credit Agreement. We incurred no early termination fees in connection with replacing the previous credit facility.
	The Credit Agreement provides for a revolving credit commitment of up to $600.0 million, of which up to $75.0 million may be used for issuances of standby or commercial letters of credit and up to $50.0 million may be used for the making of swing loans, as defined in the Credit Agreement. We may from time to time request, subject to certain conditions, an increase in the revolving credit commitment up to a maximum aggregate revolving credit commitment of $850.0 million.
	The Credit Agreement provides that we may elect that each borrowing in U.S. dollars be either base rate loans or Eurocurrency loans, as defined in the Credit Agreement. All loans denominated in currencies other than U.S. dollars will be Eurocurrency loans. Interest rates on base rate loans and outstanding drawings on letters of credit in U.S. dollars under the Credit Agreement are based on the base rate, as defined in the Credit Agreement. Interest rates on Eurocurrency loans or outstanding drawings on letters of credit in currencies other than U.S. dollars are based on an adjusted London Interbank Offered Rate (which we refer to as LIBOR), as defined in the Credit Agreement, plus a margin of 0.85%, 0.95%, 1.05%, 1.25% or 1.45%, depending on the financial leverage ratio we maintain. Interest rates on swing loans are based, at our election, on either the base rate, as defined in the Credit Agreement, or such alternate rate as may be quoted by the lead lender. The annual facility fee related to the Credit Agreement is .15%, .175%, .20%, .25% or .30% of the used and unused portions of the revolving credit commitment, depending on the financial leverage ratio we maintain. In connection with entering into the Credit Agreement, we incurred approximately $2.1 million of debt acquisition costs that were capitalized and will be amortized on a pro rata basis over the term of the Credit Agreement.
	The terms of our Credit Agreement include various financial covenants, including covenants that require us to maintain specified levels of net worth and financial leverage ratios. We were in compliance with these covenants as of September 30, 2013. The Credit Agreement also includes customary events of default, with corresponding grace periods, including, without limitation, payment defaults, cross-defaults to other agreements evidencing indebtedness and bankruptcy-related defaults.
	At September 30, 2013, $15.2 million of letters of credit (for which we had $8.7 million of liabilities recorded at September 30, 2013) were outstanding under the Credit Agreement. There were $135.5 million of borrowings outstanding under the Credit Agreement at September 30, 2013. Accordingly, as of September 30, 2013, $449.3 million remained available for potential borrowings under the Credit Agreement, of which $59.8 million may be in the form of additional letters of credit.
	See Note 12 to these unaudited consolidated financial statements for additional discussion on our contractual obligations and commitments as of September 30, 2013.
	The following is a summary of our corporate debt (in millions):
		September 30,		December 31,
		2013		2012
	Note Purchase Agreements:
	Semi-annual payments of interest, fixed rate of 6.26%, balloon due 2014	$	100	$	100
	Semi-annual payments of interest, fixed rate of 6.44%, balloon due 2017		300		300
	Semi-annual payments of interest, fixed rate of 5.85%, $50 million due in 2016, 2018 and 2019		150		150
	Semi-annual payments of interest, fixed rate of 5.18%, balloon due 2021		75		75
	Semi-annual payments of interest, fixed rate of 5.49%, balloon due 2023		50		50
	Semi-annual payments of interest, fixed rate of 3.99%, balloon due 2020		50		50
	Semi-annual payments of interest, fixed rate of 3.69%, balloon due 2022		200		—
	Total Note Purchase Agreements		925		725
	Credit Agreement:
	Periodic payments of interest and principal, prime or LIBOR plus up to 1.45%, expires September 19, 2018		135.5		129
		$	1,060.50	$	854
	The fair value of the $925.0 million in debt under the note purchase agreements at September 30, 2013 was $985.2 million due to the long-term duration and fixed interest rates associated with these debt obligations. No active or observable market exists for our private placement long-term debt. Therefore, the estimated fair value of this debt is based on discounted future cash flows, which is a Level 3 fair value measurement, using current interest rates available for debt with similar terms and remaining maturities. To estimate an all-in interest rate for discounting, we obtain market quotes for notes with the same terms as ours, which we have deemed to be the closest approximation of current market rates. We have not adjusted this rate for risk profile changes, covenant issues or credit ratings changes.

Earnings_Per_Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
Earnings Per Share	6. Earnings Per Share
	The following table sets forth the computation of basic and diluted net earnings per share (in millions, except per share data):
		Three-month period ended				Nine-month period ended
		September  30,				September  30,
		2013		2012		2013		2012
	Net earnings	$	74.6	$	61.7	$	208.6	$	161.5
	Weighted average number of common shares outstanding		129.8		123.1		127.7		119.7
	Dilutive effect of stock options using the treasury stock method		1.5		1.4		1.6		1.5
	Weighted average number of common and common equivalent shares outstanding		131.3		124.5		129.3		121.2
	Basic net earnings per share	$	0.57	$	0.5	$	1.63	$	1.35
	Diluted net earnings per share	$	0.57	$	0.5	$	1.61	$	1.33
	Options to purchase 1.7 million and 1.4 million shares of common stock were outstanding at September 30, 2013 and 2012, respectively, but were not included in the computation of the dilutive effect of stock options for the three-month periods then ended. Options to purchase 1.2 million and 1.0 million shares of common stock were outstanding at September 30, 2013 and 2012, respectively, but were not included in the computation of the dilutive effect of stock options for the nine-month periods then ended. These stock options were excluded from the computation because the options’ exercise prices were greater than the average market price of our common shares during the respective period, and therefore would be anti-dilutive to earnings per share under the treasury stock method.

Stock_Option_Plans

Stock Option Plans	9 Months Ended
	Sep. 30, 2013
Text Block [Abstract]
Stock Option Plans	7. Stock Option Plans
	Long-Term Incentive Plan
	On May 10, 2011, our stockholders approved the Arthur J. Gallagher 2011 Long-Term Incentive Plan (which we refer to as the LTIP), which replaced our previous stockholder-approved Arthur J. Gallagher & Co. 2009 Long-Term Incentive Plan (which we refer to as the 2009 LTIP). The LTIP term began May 10, 2011 and terminates on the date of the annual meeting of stockholders that occurs during 2018, unless terminated earlier by our board of directors. All of our officers, employees and non-employee directors are eligible to receive awards under the LTIP. The compensation committee of our board of directors determines the participants under the LTIP. The LTIP provides for non-qualified and incentive stock options, stock appreciation rights, restricted stock, restricted stock units and performance units, any or all of which may be made contingent upon the achievement of performance criteria. A stock appreciation right entitles the holder to receive, upon exercise and subject to withholding taxes, cash or shares of our common stock (which may be restricted stock) with a value equal to the difference between the fair market value of our common stock on the exercise date and the base price of the stock appreciation right. Subject to the LTIP limits, the compensation committee has the discretionary authority to determine the size of an award.
	Shares of our common stock available for issuance under the LTIP include authorized and unissued shares of common stock or authorized and issued shares of common stock reacquired and held as treasury shares or otherwise, or a combination thereof. The number of available shares will be reduced by the aggregate number of shares that become subject to outstanding awards granted under the LTIP. To the extent that shares subject to an outstanding award granted under either the LTIP or the 2009 LTIP are not issued or delivered by reason of the expiration, termination, cancellation or forfeiture of such award or by reason of the settlement of such award in cash, then such shares will again be available for grant under the LTIP. Shares that are subject to a stock appreciation right and were not issued upon the net settlement or net exercise of such stock appreciation right, shares that are used to pay the exercise price of an option, delivered to or withheld by us to pay withholding taxes, and shares that are purchased on the open market with the proceeds of an option exercise, may not again be made available for issuance.
	The maximum number of shares available under the LTIP for restricted stock, restricted stock unit awards and performance unit awards settled with stock (i.e., all awards other than stock options and stock appreciation rights) is 0.5 million at September 30, 2013. To the extent necessary to be qualified performance-based compensation under Section 162(m) of the Internal Revenue Code (which we refer to as the IRC): (i) the maximum number of shares with respect to which options or stock appreciation rights or a combination thereof that may be granted during any fiscal year to any person is 200,000; (ii) the maximum number of shares with respect to which performance-based restricted stock or restricted stock units that may be granted during any fiscal year to any person is 100,000; and (iii) the maximum amount that may be payable with respect to performance units granted during any fiscal year to any person is $3.0 million.
	The LTIP provides for the grant of stock options, which may be either tax-qualified incentive stock options or non-qualified options and stock appreciation rights. The compensation committee determines the period for the exercise of a non-qualified stock option, tax-qualified incentive stock option or stock appreciation right, provided that no option can be exercised later than seven years after its date of grant. The exercise price of a non-qualified stock option or tax-qualified incentive stock option and the base price of a stock appreciation right cannot be less than 100% of the fair market value of a share of our common stock on the date of grant, provided that the base price of a stock appreciation right granted in tandem with an option will be the exercise price of the related option.
	Upon exercise, the option exercise price may be paid in cash, by the delivery of previously owned shares of our common stock, through a net-exercise arrangement, or through a broker-assisted cashless exercise arrangement. The compensation committee determines all of the terms relating to the exercise, cancellation or other disposition of an option or stock appreciation right upon a termination of employment, whether by reason of disability, retirement, death or any other reason. Stock option and stock appreciation right awards under the LTIP are non-transferable.
	On March 13, 2013, the compensation committee granted 1,665,000 options to our officers and key employees that become exercisable at the rate of 34%, 33% and 33% on the anniversary date of the grant in 2016, 2017 and 2018, respectively. On March 16, 2012, the compensation committee granted 1,355,000 options to our officers and key employees that become exercisable at the rate of 34%, 33% and 33% on the anniversary date of the grant in 2015, 2016 and 2017, respectively. The 2013 and 2012 options expire seven years from the date of grant, or earlier in the event of certain terminations of employment. For certain of our executive officers age 55 or older, stock options awarded in 2013 are no longer subject to forfeiture upon such officers’ departure from the company after two years from the date of grant.
	Other Information
	All of our stock option plans provide for the immediate vesting of all outstanding stock option grants in the event of a change in control of our company, as defined in the applicable plan documents.
	During the three-month periods ended September 30, 2013 and 2012, we recognized $2.2 million and $2.2 million, respectively, of compensation expense related to our stock option grants. During the nine-month periods ended September 30, 2013 and 2012, we recognized $5.4 million and $5.2 million, respectively, of compensation expense related to our stock option grants.
	For purposes of expense recognition, the estimated fair values of the stock option grants are amortized to expense over the options’ vesting period. We estimated the fair value of stock options at the date of grant using the Black-Scholes option pricing model with the following weighted average assumptions:
		2013				2012
	Expected dividend yield		3.5	%			4	%
	Expected risk-free interest rate		1.2	%			1.2	%
	Volatility		29.6	%			26.7	%
	Expected life (in years)		6				5
	Option valuation models require the input of highly subjective assumptions including the expected stock price volatility. The Black-Scholes option pricing model was developed for use in estimating the fair value of traded options which have no vesting restrictions and are fully transferable. Because our employee and director stock options have characteristics significantly different from those of traded options, and because changes in the selective input assumptions can materially affect the fair value estimate, in management’s opinion, the existing models do not necessarily provide a reliable single measure of the fair value of our employee and non-employee director stock options. The weighted average fair value per option for all options granted during the nine-month periods ended September 30, 2013 and 2012, as determined on the grant date using the Black-Scholes option pricing model, was $7.51 and $5.49, respectively.
	The following is a summary of our stock option activity and related information for 2013 (in millions, except exercise price and year data):
		Nine-month period ended September 30, 2013
										Weighted
										Average
						Weighted				Remaining
		Shares				Average				Contractual				Aggregate
		Under				Exercise				Term				Intrinsic
		Option				Price				(in years)				Value
	Beginning balance		9			$	28.8
	Granted		1.6				39.17
	Exercised		(2.1	)			27
	Forfeited or canceled		—				—
	Ending balance		8.5			$	31.29				3.83			$	105
	Exercisable at end of period		3.9			$	27.67				2.38			$	62.9
	Ending vested and expected to vest		8.4			$	31.2				3.8			$	104.2
	Options with respect to 8.0 million shares (less any shares of restricted stock issued under the LTIP—see Note 9 to these unaudited consolidated financial statements) were available for grant under the LTIP at September 30, 2013.
	The total intrinsic value of options exercised during the nine-month periods ended September 30, 2013 and 2012 was $28.8 million and $19.1 million, respectively. As of September 30, 2013, we had approximately $23.0 million of total unrecognized compensation expense related to nonvested options. We expect to recognize that expense over a weighted average period of approximately four years.
	Other information regarding stock options outstanding and exercisable at September 30, 2013 is summarized as follows (in millions, except exercise price and year data):
				Options Outstanding												Options Exercisable
	Range of Exercise Prices			Number				Weighted				Weighted				Number		Weighted
				Outstanding				Average				Average				Exercisable		Average
								Remaining				Exercise						Exercise
								Contractual				Price						Price
								Term
								(in years)
	$ 10.58 - $ 27.25				2.9				2.78			$	25.87				2.1	$	25.88
	27.35 - 30.95				2.4				2.56				29.73				1.7		29.44
	31.24 - 35.71				1.5				4.92				35.4				0.1		32.95
	35.95 - 35.95				—				5.84				35.95				—		—
	39.17 - 39.17				1.7				6.45				39.17				—		—
	$ 10.58 - $ 39.17				8.5				3.83			$	31.29				3.9	$	27.67

Deferred_Compensation

Deferred Compensation	9 Months Ended
	Sep. 30, 2013
Compensation And Retirement Disclosure [Abstract]
Deferred Compensation	8. Deferred Compensation
	We have a Deferred Equity Participation Plan, which is a non-qualified plan that generally provides for distributions to certain of our key executives when they reach age 62 (or the one-year anniversary of the date of the grant for participants over the age of 61 as of the grant date) or upon or after their actual retirement. Under the provisions of the plan, we typically contribute shares of our common stock or cash, in an amount approved by the compensation committee, to a rabbi trust on behalf of the executives participating in the plan. Alternatively, we may contribute cash to the rabbi trust and instruct the trustee to acquire a specified number of shares of our common stock on the open market or in privately negotiated transactions. Distributions under the plan may not normally be made until the participant reaches age 62 (or the one-year anniversary of the date of the grant for participants over the age of 61 as of the grant date) and are subject to forfeiture in the event of voluntary termination of employment prior to then. All contributions to the plan deemed to be invested in shares of our common stock are distributed in the form of our common stock and all other distributions are paid in cash.
	Our common stock that is issued to or purchased by the rabbi trust as a contribution under the Plan is valued at historical cost, which equals its fair market value at the date of grant or date of purchase. When common stock is issued or purchased, we record an unearned deferred compensation obligation as a reduction of capital in excess of par value in the accompanying consolidated balance sheet, which is amortized to compensation expense ratably over the vesting period of the participants. Future changes in the fair market value of our common stock owed to the participants do not have any impact on the amounts recorded in our consolidated financial statements.
	In the first quarter of each of 2013 and 2012, the compensation committee approved $8.0 million and $7.3 million, respectively, of cash awards in the aggregate to certain key executives under the Deferred Equity Participation Plan that were contributed to the rabbi trust in second quarter 2013 and first quarter 2012, respectively. The fair value of the funded cash award assets at December 31, 2012 was $41.6 million and has been included in other noncurrent assets in the accompanying consolidated balance sheet. In the second quarter of 2013, we instructed the trustee for the Plan to liquidate all investments held under the Plan, other than our common stock, and use the proceeds to purchase additional shares of our common stock on the open market. As a result, the Plan sold all of the funded cash award assets and purchased 1.2 million shares of our common stock at an aggregate cost of $52.4 million during the second quarter of 2013. During the three-month periods ended September 30, 2013 and 2012, we charged $2.0 million and $1.5 million, respectively, to compensation expense related to these awards. During the nine-month periods ended September 30, 2013 and 2012, we charged $5.3 million and $4.1 million, respectively, to compensation expense related to these awards.
	At September 30, 2013 and December 31, 2012, we recorded $30.0 million (related to 2.0 million shares) and $5.6 million (related to 0.8 million shares), respectively, of unearned deferred compensation as a reduction of capital in excess of par value in the accompanying consolidated balance sheet. The total intrinsic value of our unvested equity based awards under the plan at September 30, 2013 and December 31, 2012 was $89.2 million and $21.1 million, respectively. During each of the nine-month periods ended September 30, 2013 and 2012, cash and equity awards with an aggregate fair value of $0.7 million were vested and distributed to executives under this plan.

Restricted_Stock_and_Cash_Awar

Restricted Stock and Cash Awards	9 Months Ended
	Sep. 30, 2013
Text Block [Abstract]
Restricted Stock and Cash Awards	9. Restricted Stock and Cash Awards
	Restricted Stock Awards
	As discussed in Note 7 to these unaudited consolidated financial statements, on May 10, 2011, our stockholders approved the LTIP, which replaced our previous stockholder-approved 2009 LTIP. The LTIP provides for the grant of a stock award either as restricted stock or as restricted stock units. In either case, the compensation committee may determine that the award will be subject to the attainment of performance measures over an established performance period. Stock awards are non-transferable and subject to forfeiture if the holder does not remain continuously employed with us during the applicable restriction period or, in the case of a performance-based award, if applicable performance measures are not attained. The compensation committee will determine all of the terms relating to the satisfaction of performance measures and the termination of a restriction period, or the forfeiture and cancellation of a restricted stock award upon a termination of employment, whether by reason of disability, retirement, death or any other reason. The compensation committee may grant unrestricted shares of common stock or units representing the right to receive shares of common stock to employees who have attained age 62.
	The agreements awarding restricted stock units will specify whether such award may be settled in shares of our common stock, cash or a combination of shares and cash and whether the holder will be entitled to receive dividend equivalents, on a current or deferred basis, with respect to such award. Prior to the settlement of a restricted stock unit, the holder of a restricted stock unit will have no rights as a stockholder of the company. The maximum number of shares available under the LTIP for restricted stock, restricted stock units and performance unit awards settled with stock (i.e., all awards other than stock options and stock appreciation rights) is 1.2 million. At September 30, 2013, 0.5 million shares were available for grant under the LTIP for such awards.
	In the first quarter of each of 2013 and 2012, we granted 345,000 and 332,000 restricted stock units, respectively, to employees under the LTIP, with an aggregate fair value of $13.5 million and $11.9 million, respectively, at the date of grant. These 2013 and 2012 awards of restricted stock units vest as follows: 345,000 units granted in first quarter 2013 and 332,000 units granted in first quarter 2012, vest in full based on continued employment through March 13, 2017 and March 16, 2016, respectively. In the second quarter of each of 2013 and 2012, we granted 17,500 and 20,000 restricted stock units, respectively, to non-employee Board of Directors under the LTIP, with an aggregate fair value of $0.8 million and $0.7 million, respectively, at the date of grant. These grants vest in full one year from the date of grant. For certain of our executive officers age 55 or older, restricted stock units awarded in 2013 are no longer subject to forfeiture upon such officers’ departure from the company after two years from the date of grant.
	We account for restricted stock awards at historical cost, which equals their fair market value at the date of grant. When restricted stock units are granted, no amounts are recorded in the accompanying consolidated financial statements. The grant date fair market value is amortized to compensation expense ratably over the vesting period of the participants with the offsetting amount recorded in capital in excess of par in the consolidated balance sheet. Future changes in the fair value of our common stock that is owed to the participants do not have any direct impact on the amounts recorded in our consolidated financial statements. During the three-month periods ended September 30, 2013 and 2012, we charged $2.3 million and $1.7 million, respectively, to compensation expense related to restricted stock unit awards granted in 2006 through 2013. During the nine-month periods ended September 30, 2013 and 2012, we charged $7.4 million and $5.5 million, respectively, to compensation expense related to restricted stock unit awards granted in 2006 through 2013. The total intrinsic value of unvested restricted stock units at September 30, 2013 and 2012 was $46.4 million and $33.8 million, respectively. During the nine-month periods ended September 30, 2013 and 2012, equity awards (including accrued dividends) with an aggregate fair value of $8.4 million and $7.2 million were vested and distributed to employees under this plan.
	Cash Awards
	On March 13, 2013, pursuant to our Performance Unit Program (which we refer to as the Program), the compensation committee approved provisional cash awards of $10.5 million in the aggregate for future grant to our officers and key employees that are denominated in units (269,000 units in the aggregate), each of which was equivalent to the value of one share of our common stock on the date the provisional award was approved. The Program consists of a one-year performance period based on our financial performance and a two-year vesting period. At the discretion of the compensation committee and determined based on our performance, the eligible officer or key employee will be granted a percentage of the provisional cash award units that equates to the EBITAC growth achieved (as defined in the Program). At the end of the performance period, eligible participants will be granted a number of units based on achievement of the performance goal and subject to approval by the compensation committee. Granted units for the 2013 provisional award will fully vest based on continuous employment through January 1, 2016. For certain of our executive officers age 55 or older, awards granted under the Program in 2013 are no longer subject to forfeiture upon such officers’ departure from the company after two years from the date of grant. The ultimate award value will be equal to the trailing twelve-month stock price on December 31, 2015, multiplied by the number of units subject to the award, but limited to between 0.5 and 1.5 times the original value of the units determined as of the grant date. The fair value of the awarded units will be paid out in cash as soon as practicable in 2016. If an eligible employee leaves us prior to the vesting date, the entire award will be forfeited. We did not recognize any compensation expense during the nine-month period ended September 30, 2013 related to the 2013 provisional award under the Program.
	On March 16, 2012, pursuant to the Program, the compensation committee approved provisional cash awards of $13.1 million in the aggregate for future grant to our officers and key employees that are denominated in units (368,000 units in the aggregate), each of which was equivalent to the value of one share of our common stock on the date the provisional award was approved. Terms of the 2012 provisional award were similar to the terms for the 2013 provisional award. Based on our performance for 2012, we granted 365,000 units under the Program in first quarter 2013 that will fully vest on January 1, 2015. During the three-month period ended September 30, 2013, we charged $2.0 million to compensation expense related to these awards. During the nine-month period ended September 30, 2013, we charged $5.4 million to compensation expense related to the 2012 awards.
	On March 8, 2011, pursuant to the Program, the compensation committee approved provisional cash awards of $14.4 million in the aggregate for future grant to our officers and key employees that are denominated in units (464,000 units in the aggregate), each of which was equivalent to the value of one share of our common stock on the date the provisional award was approved. Terms of the 2011 provisional award were similar to the terms for the 2013 provisional award. Based on our performance for 2011, we granted 432,000 units under the Program in first quarter 2012 that will fully vest on January 1, 2014. During the three-month periods ended September 30, 2013 and 2012, we charged $2.6 million and $1.9 million, respectively, to compensation expense related to these awards. During the nine-month periods ended September 30, 2013 and 2012, we charged $6.9 million and $5.7 million, respectively, to compensation expense related to the 2011 awards.
	On March 2, 2010, pursuant to the Program, the compensation committee approved provisional cash awards of $17.0 million in the aggregate for future grant to our officers and key employees that are denominated in units (706,000 units in the aggregate), each of which was equivalent to the value of one share of our common stock on the date the provisional award was approved. Terms of the 2010 provisional award were similar to the terms for the 2013 provisional award. However, based on company performance for 2010, we did not grant any units in 2011 related to the 2010 provisional award under the Program. We did not recognize any compensation expense during 2013 or 2012 related to the 2010 provisional award.
	During the nine-month period ended September 30, 2012, cash awards related to the 2009 provisional award with an aggregate fair value of $26.5 million (1.1 million units in the aggregate) were vested and distributed to employees under the Program.

Retirement_Plans

Retirement Plans	9 Months Ended
	Sep. 30, 2013
Compensation And Retirement Disclosure [Abstract]
Retirement Plans	10. Retirement Plans
	We have a noncontributory defined benefit pension plan that, prior to July 1, 2005, covered substantially all of our domestic employees who had attained a specified age and one year of employment. Benefits under the plan were based on years of service and salary history. In 2005, we amended our defined benefit pension plan to freeze the accrual of future benefits for all U.S. employees, effective on July 1, 2005. In the table below, the service cost component represents plan administration costs that are incurred directly by the plan.
	The components of the net periodic pension benefit cost for the plan consists of the following (in millions):
		Three-month period ended						Nine-month period ended
		September 30,						September 30,
		2013			2012			2013			2012
	Service cost	$	0.2		$	0.1		$	0.4		$	0.3
	Interest cost on benefit obligation		2.9			3			8.8			9
	Expected return on plan assets		(4.2	)		(3.8	)		(12.8	)		(11.4	)
	Amortization of net actuarial loss		2			1.8			5.9			5.4
	Net periodic benefit cost	$	0.9		$	1.1		$	2.3		$	3.3
	We are not required under the IRC to make any minimum contributions to the plan for the 2013 plan year. We were also not required under the IRC to make any minimum contributions for the 2012 plan year. This level of required funding is based on the plan being frozen and the aggregate amount of our historical funding. During the nine-month periods ended September 30, 2013 and 2012, we made discretionary contributions of $6.3 million and $5.4 million to the plan.

Investments

Investments	9 Months Ended
	Sep. 30, 2013
Equity Method Investments And Joint Ventures [Abstract]
Investments	11. Investments
	The following is a summary of our investments and the related funding commitments (in millions):
			30-Sep-13				December 31,
					Funding		2012
			Assets		Commitments		Assets
	Chem-Mod LLC		$	4	$	—	$	4
	Chem-Mod International LLC			2		—		2
	C-Quest Technology LLC			2		—		—
	Clean-coal investments
	Non-controlling interest in four limited liability companies that own nine 2009 Era Clean Coal Plants			8.2		1.8		2.8
	Controlling interest in two limited liability companies that own five 2009 Era Clean Coal Plants			6.8		0.9		6.3
	Non-controlling interest in six limited liability companies that own five 2011 Era Clean Coal Plants			12.1		—		13.2
	Controlling interest in five limited liability companies that own nine 2011 Era Clean Coal Plants			41.4		2.2		9.2
	Controlling interest in a limited liability company that owns six 2011 Era Clean Coal Plants			7.4		0.7		5.1
	Notes receivable and interest from co-investor related to the sales of three 2009 Era Plants			—		—		8.5
	Other investments			3.6		5		3
	Total investments		$	87.5	$	10.6	$	54.1
	Chem-Mod LLC - At September 30, 2013, we held a 46.54% controlling interest in Chem-Mod LLC. Chem-Mod LLC possesses the exclusive marketing rights, in the U.S. and Canada, for technologies used to reduce emissions created during the combustion of coal. The refined coal production plants discussed below, as well as those owned by other unrelated parties, license and use Chem-Mod’s proprietary technologies, The Chem-Mod™ Solution, in the production of refined coal. The Chem-Mod™ Solution uses a dual injection sorbent system to reduce mercury, sulfur dioxide and other emissions at coal-fired power plants.
	We believe that the application of The Chem-Mod™ Solution qualifies for refined coal tax credits under IRC Section 45 when used with refined coal production plants placed in service by December 31, 2011 or 2009. Chem-Mod has been marketing its technologies principally to coal-fired power plants owned by utility companies, including those utilities that are operating with the IRC Section 45 refined coal production plants in which we hold an investment.
	Chem-Mod is determined to be a variable interest entity (which we refer to as a VIE). We are the controlling manager of Chem-Mod and therefore consolidate its operations into our consolidated financial statements. At September 30, 2013, total assets and total liabilities of this VIE included in our consolidated balance sheet were $6.1 million and $0.6 million, respectively. For the nine-month period ended September 30, 2013, total revenues and expenses were $27.1 million and $15.2 million (including non-controlling interest of $13.7 million), respectively. We are under no obligation to fund Chem-Mod’s operations in the future.
	Chem-Mod International LLC - At September 30, 2013, we held a 31.52% non- controlling interest in Chem-Mod International LLC. Chem-Mod International LLC has the rights to market The Chem-Mod™ Solution in countries other than the U.S. and Canada. Such marketing activity has been limited to date.
	C-Quest Technology LLC - At September 30, 2013, we held a non-controlling 8% interest in C-Quest’s global operation. C-Quest possesses rights, information and technology for the reduction of carbon dioxide emissions created by burning fossil fuels. Thus far, C-Quest’s operations have been limited to laboratory testing. C-Quest is determined to be a VIE, but due to our lack of control over the operation of C-Quest, we do not consolidate this investment into our consolidated financial statements. We also have options to acquire an additional 19% interest in C-Quest’s global operations for $9.5 million at any time on or prior to August 15, 2016. On August 1, 2013, we loaned the majority owner $2.0 million at a 2% interest rate, which matures on May 15, 2014. The loan can be paid in cash or by delivery of an additional 4% ownership interest in C-Quest’s global operations. If the loan is paid by delivery of the additional 4% ownership interest, our option would be reduced to 15% and the remaining purchase price would be reduced to $7.5 million.
	Clean Coal Investments -
		•		We have investments in limited liability companies that own 34 refined coal production plants which produce refined coal using propriety technologies owned by Chem-Mod. We believe the production and sale of refined coal at these plants is qualified to receive refined coal tax credits under IRC Section 45. The fourteen plants placed in service prior to December 31, 2009 (which we refer to as the 2009 Era Plants) can receive tax credits through 2019 and the twenty plants placed in service prior to December 31, 2011 (which we refer to as the 2011 Era Plants) can receive tax credits through 2021.
		•		On March 1, 2013, we purchased an additional ownership interest in twelve of the 2009 Era Plants from one of the co-investors. For nine of the plants, our ownership increased from 24.5% to 49.5%. Our investment in these plants had been accounted for under the equity method of accounting and will continue to be accounted for under the equity method. For three of the plants, our ownership went from 25.0% to 60.0%. Our investment in these plants had been accounted for under the equity method of accounting. As of March 1, 2013, we consolidated the operations of the limited liability company that owns these three plants. Total revenues and expenses recorded in our unaudited consolidated statement of earnings for the nine-month period ended September 30, 2013 related to this acquisition were $68.4 million and $72.3 million, respectively.
		•		Our purchase price for the additional ownership interests in these twelve plants was the assumption of the promissory note that we received as consideration for the co-investor’s purchase of ownership interests in three of the 2009 Era Plants on March 1, 2010, which had a carrying value, including accrued interest, of $8.0 million at March 1, 2013, plus the payment of cash and other consideration of $5.0 million. We recognized a gain of $9.6 million, which included the increase in fair value of our prior 25% equity interest in the limited liability company upon the acquisition of the additional 35% equity interest, and recorded $26.3 million of fixed and other amortizable intangible assets and $5.0 million of other assets in connection with this transaction. The carrying value of our prior non-controlling interest in the limited liability company was $4.8 million as of the acquisition date. The fair value of our prior non-controlling interest in the limited liability company was determined by allocating, on a pro rata basis, the fair value of the limited liability company as adjusted for our lack of control in our prior ownership position. We determined the fair value of the limited liability company based on provisional estimates of fair value using similar valuation techniques to those discussed in Note 3 to these unaudited consolidated financial statements.
		•		On September 1, 2013, we purchased a 99% interest in a limited liability company that has ownership interests in four limited liability companies that own five 2011 Era Plants. The purchase price was $4.0 million in cash plus a $10.0 million note with 3% interest due in installments through December 19, 2021. Total revenues and expenses recorded in our unaudited consolidated statement of earnings, for the nine-month period ended September 30, 2013 related to the acquisition, were $6.3 million and $6.9 million, respectively.
		•		As of September 30, 2013:
		•		Twenty-eight of the plants have long-term production contracts.
		•		The remaining six plants are in various stages of seeking and negotiating long-term production contracts, permitting and construction of permanent deployment facilities.
		•		We have a non-controlling, minority interest in fourteen plants. We also have agreements in principle with co-investors for the sale of majority ownership interests in six additional plants. We may sell ownership interests in some or all of the remaining plants to co-investors.
		•		Nine of the 2009 Era Plants and five of the 2011 Era Plants are owned by limited liability companies, which we have determined to be VIEs, for which we are not the primary beneficiary. At September 30, 2013, total assets and total liabilities of these VIEs were $80.4 million and $37.8 million, respectively. For the nine-month period ended September 30, 2013, total revenues and expenses of these VIEs were $255.7 million and $291.9 million, respectively.
		•		In all limited liability companies where we are a non-controlling, minority investor, the membership agreements for the operations of each of these entities contain provisions that preclude an individual member from being able to make major decisions that would denote control. As of the date we became a non-controlling, minority investor, we deconsolidated these entities and subsequently accounted for the investments using equity method accounting.
		•		For all plants that are not under long-term production contracts, we estimate that we will invest, on average, an additional $5.0 million per plant to connect and house each of them. For those plants that will have majority ownership co-investors, the average additional investment will be $2.5 million. We plan to sell majority ownership interests in such plants to co-investors and relinquish control of the plants, thereby becoming a non-controlling, minority investor. We are currently committed to fund an additional $5.6 million under engineering and construction contracts related to moving, connecting and housing the refined coal plants that we plan to redeploy during the remainder of 2013. Subsequent to 2013, we estimate that we will invest an additional $30.0 million to $35.0 million to redeploy the remainder of the refined coal plants before co-investor contributions.
		•		Each investor funds its portion of the on-going operations of the limited liability companies in proportion to its investment ownership percentage. Other than our portion of the on-going operational funding, there are no additional amounts that we are committed to related to funding these investments.
		•		We are aware that some of the coal-fired power plants that purchase the refined coal are considering changing to burning natural gas or shutting down completely for economic reasons. We and our partners are prepared to move the refined coal productions plants to other, generally higher volume, coal-fired power plants. If these potential developments were to occur, we estimate those plants will not operate for 12 to 18 months during their movement and redeployment, which could have a material impact on the amount of tax credits that are generated by these plants.
		•		Until March 1, 2013, we had a promissory note from a co-investor that was received as part of the consideration for the March 1, 2010 sale of ownership interests in three of the 2009 Era Plants. This note was assumed by us as part of our purchase of additional ownership interests in twelve of the 2009 Era Plants as described above.
	Other Investments - At September 30, 2013, we owned a non-controlling, minority interest in five venture capital funds totaling $3.2 million, a 20% non-controlling interest in an investment management company totaling $0.5 million, twelve certified low-income housing developments with zero carrying value and two real estate entities with zero carrying value. The low-income housing developments and real estate entities have been determined to be VIEs, but are not required to be consolidated due to our lack of control over their respective operations. At September 30, 2013, total assets and total debt of these VIEs were approximately $60.0 million and $20.0 million, respectively.

Commitments_Contingencies_and_

Commitments, Contingencies and Off-Balance Sheet Arrangements	9 Months Ended
	Sep. 30, 2013
Commitments And Contingencies Disclosure [Abstract]
Commitments, Contingencies and Off-Balance Sheet Arrangements	12. Commitments, Contingencies and Off-Balance Sheet Arrangements
	In connection with our investing and operating activities, we have entered into certain contractual obligations and commitments. See Notes 5 and 11 to these unaudited consolidated financial statements for additional discussion of these obligations and commitments. Our future minimum cash payments, including interest, associated with our contractual obligations pursuant to the note purchase agreements and Credit Agreement, operating leases and purchase commitments at September 30, 2013 were as follows (in millions):
		Payments Due by Period
	Contractual Obligations	2013			2014			2015			2016			2017		Thereafter		Total
	Note purchase agreements	$	—		$	100		$	—		$	50		$	300	$	475	$	925
	Credit Agreement		135.5			—			—			—			—		—		135.5
	Interest on debt		8.1			50.4			44.1			44.1			41.2		76.6		264.5
	Total debt obligations		143.6			150.4			44.1			94.1			341.2		551.6		1,325.00
	Operating lease obligations		18.8			69.4			61.8			50.6			40.2		109.3		350.1
	Less sublease arrangements		(2.1	)		(1.8	)		(0.8	)		(0.1	)		—		—		(4.8	)
	Outstanding purchase obligations		4.1			9.4			7			1.3			0.3		—		22.1
	Total contractual obligations	$	164.4		$	227.4		$	112.1		$	145.9		$	381.7	$	660.9	$	1,692.40
	The amounts presented in the table above may not necessarily reflect our actual future cash funding requirements, because the actual timing of the future payments made may vary from the stated contractual obligation.
	Note Purchase Agreements and Credit Agreement - See Note 5 to these unaudited consolidated financial statements for a discussion of the terms of the note purchase agreements and the Credit Agreement.
	Operating Lease Obligations - Our corporate segment’s executive offices and certain subsidiary and branch facilities of our brokerage and risk management segments are located at Two Pierce Place, Itasca, Illinois, where we lease approximately 306,000 square feet of space, or approximately 60% of the building. The lease commitment on this property expires February 28, 2018.
	We generally operate in leased premises at our other locations. Certain of these leases have options permitting renewals for additional periods. In addition to minimum fixed rentals, a number of leases contain annual escalation clauses which are generally related to increases in an inflation index.
	We have leased certain office space to several non-affiliated tenants under operating sublease arrangements. In the normal course of business, we expect that the leases will not be renewed or replaced. We adjust charges for real estate taxes and common area maintenance annually based on actual expenses, and we recognize the related revenues in the year in which the expenses are incurred. These amounts are not included in the minimum future rentals to be received in the contractual obligations table above.
	Outstanding Purchase Obligations - As a service company, we typically do not have a material amount of outstanding purchase obligations at any point in time. The amount disclosed in the contractual obligations table above represents the aggregate amount of unrecorded purchase obligations that we had outstanding at September 30, 2013. These obligations represent agreements to purchase goods or services that were executed in the normal course of business.
	Off-Balance Sheet Commitments - Our total unrecorded commitments associated with outstanding letters of credit, financial guarantees and funding commitments as of September 30, 2013 were as follows (in millions):
																		Total
		Amount of Commitment Expiration by Period																Amounts
	Off-Balance Sheet Commitments	2013			2014			2015			2016			2017		Thereafter		Committed
	Letters of credit	$	—		$	—		$	—		$	—		$	—	$	15.2	$	15.2
	Financial guarantees		—			—			—			—			—		9.3		9.3
	Funding commitments		7			0.7			—			—			—		2.9		10.6
	Total commitments	$	7		$	0.7		$	—		$	—		$	—	$	27.4	$	35.1
	Since commitments may expire unused, the amounts presented in the table above do not necessarily reflect our actual future cash funding requirements. See Note 11 to these unaudited consolidated financial statements for a discussion of our funding commitments related to our corporate segment and the Off-Balance Sheet Debt section below for a discussion of our letters of credit. All of the letters of credit represent multiple year commitments that have annual, automatic renewing provisions and are classified by the latest commitment date.
	Since January 1, 2002, we have acquired 265 companies, all of which were accounted for using the acquisition method for recording business combinations. Substantially all of the purchase agreements related to these acquisitions contain provisions for potential earnout obligations. For all of our acquisitions made in the period from 2009 to 2013 that contain potential earnout obligations, such obligations are measured at fair value as of the acquisition date and are included on that basis in the recorded purchase price consideration for the respective acquisition. The amounts recorded as earnout payables are primarily based upon estimated future operating results of the acquired entities over a two- to three-year period subsequent to the acquisition date. The aggregate amount of the maximum earnout obligations related to these acquisitions was $400.4 million, of which $140.4 million was recorded in our consolidated balance sheet as of September 30, 2013 based on the estimated fair value of the expected future payments to be made.
	Off-Balance Sheet Debt - Our unconsolidated investment portfolio includes investments in enterprises where our ownership interest is between 1% and 50%, in which management has determined that our level of influence and economic interest is not sufficient to require consolidation. As a result, these investments are accounted for under the equity method. None of these unconsolidated investments had any outstanding debt at September 30, 2013 or December 31, 2012 that was recourse to us.
	At September 30, 2013, we had posted two letters of credit totaling $9.5 million, in the aggregate, related to our self-insurance deductibles, for which we had a recorded liability of $8.7 million. We have an equity investment in a rent-a-captive facility, which we use as a placement facility for certain of our insurance brokerage operations. At September 30, 2013, we had posted two letters of credit totaling $5.7 million to allow the rent-a-captive facility to meet minimum statutory surplus requirements and for additional collateral related to premium and claim funds held in a fiduciary capacity. These letters of credit have never been drawn upon.
	Litigation - We are the defendant in various legal actions related to employment matters and otherwise incidental to the nature of our business. We believe we have meritorious defenses and intend to defend ourselves vigorously in all unresolved legal actions. In addition, we are the plaintiff in certain legal actions with and relating to former employees regarding alleged breaches of non-compete or other restrictive covenants, theft of trade secrets, breaches of fiduciary duties and related causes of action. Neither the outcomes of these legal actions nor their effect upon our business, financial condition or results of operations can be determined at this time.
	Contingent Liabilities - We purchase insurance to provide protection from errors and omissions (which we refer to as E&O) claims that may arise during the ordinary course of business. We currently retain the first $5.0 million of each and every E&O claim. Our E&O insurance provides aggregate coverage for E&O losses up to $175.0 million in excess of our retained amounts. We have historically maintained self-insurance reserves for the portion of our E&O exposure that is not insured. We periodically determine a range of possible reserve levels using actuarial techniques that rely heavily on projecting historical claim data into the future. Our E&O reserve in the September 30, 2013 consolidated balance sheet is above the lower end of the most recently determined actuarial range by $1.7 million and below the upper end of the actuarial range by $4.9 million. We can make no assurances that the historical claim data used to project the current reserve levels will be indicative of future claim activity. Thus, the E&O reserve level and corresponding actuarial range could change in the future as more information becomes known, which could materially impact the amounts reported and disclosed herein.
	Tax-advantaged Investments No Longer Held - Between 1996 and 2007, we developed and then sold portions of our ownership in various energy related investments, many of which qualified for tax credits under IRC Section 29. In connection with the sales to other investors, we provided various indemnities. At September 30, 2013, the maximum potential amount of future payments that we could be required to make under these indemnification totaled approximately $45.0 million, net of the applicable income tax benefit. In addition, we recorded tax benefits in connection with our ownership in these investments. At September 30, 2013, we had exposure on $130.0 million of previously earned tax credits. In 2004, 2007 and 2009, the IRS examined several of these investments and all examinations were closed without any changes being proposed by the IRS. However, any future adverse tax audits, administrative rulings or judicial decisions could disallow previously claimed tax credits or cause us to be subject to liability under our indemnification obligations. Because of the contingent nature of these exposures, no liabilities have been recorded in our September 30, 2013 consolidated balance sheet related to these indemnification obligations.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]
Accumulated Other Comprehensive Loss	13. Accumulated Other Comprehensive Loss
	The after-tax components of our accumulated other comprehensive loss consist of the following:
		Pension			Foreign			Fair Value of			Accumulated
		Liability			Currency			Derivative			Comprehensive
					Translation			Investments			Loss
	Balance as of December 31, 2012	$	(52.4	)	$	20.5		$	(0.9	)	$	(32.8	)
	Net change in period		0.4			(9.9	)		0.5			(9.0	)
	Balance as of September 30, 2013	$	(52.0	)	$	10.6		$	(0.4	)	$	(41.8	)
	The foreign currency translation during the nine-month period ended September 30, 2013 primarily relates to the net impact of changes in the value of the local currencies relative to the U.S. dollar for our operations in Australia, Canada, the Caribbean, India, Singapore, New Zealand and the U.K.
	During the nine-month periods ended September 30, 2013 and 2012, $5.9 million and $5.4 million, respectively, of expense related to the pension liability was reclassified from accumulated other comprehensive loss to compensation expense in the statement of earnings. During the nine-month period ended September 30, 2013, $0.6 million of expense related to the fair value of derivative investments was reclassified from accumulated other comprehensive loss to the statement of earnings. During the nine-month period ended September 30, 2012, $0.1 million of expense related to the fair value of derivative investments was reclassified from accumulated other comprehensive loss to the statement of earnings. During the nine-month periods ended September 30, 2013 and 2012, no amounts related to foreign currency translation were reclassified from accumulated other comprehensive loss to the statement of earnings.

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]
Segment Information	14. Segment Information
	We have three reportable segments: brokerage, risk management and corporate.
	The brokerage segment is primarily comprised of our retail and wholesale insurance brokerage operations. The brokerage segment generates revenues through commissions paid by insurance underwriters and through fees charged to our clients. Our brokers, agents and administrators act as intermediaries between insurers and their customers and we do not assume underwriting risks.
	The risk management segment provides contract claim settlement and administration services for enterprises that choose to self-insure some or all of their property/casualty coverages and for insurance companies that choose to outsource some or all of their property/casualty claims departments. These operations also provide claims management, loss control consulting and insurance property appraisal services. Revenues are principally generated on a negotiated per-claim or per-service fee basis.
	The corporate segment manages our clean energy and other investments. This segment also holds all of our corporate debt.
	Allocations of investment income and certain expenses are based on reasonable assumptions and estimates primarily using revenue, headcount and other information. We allocate the provision for income taxes to the brokerage and risk management segments as if those segments were preparing income tax provisions on a separate company basis. Reported operating results by segment would change if different methods were applied.
	Financial information relating to our segments for the three-month and nine-month periods ended September 30, 2013 and 2012 is as follows (in millions):
		Three-month period						Nine-month period
		ended September 30,						ended September 30,
		2013			2012			2013			2012
	Brokerage
	Total revenues	$	546.3		$	479.7		$	1,551.60		$	1,338.50
	Earnings before income taxes	$	97.3		$	82		$	250.5		$	203.8
	Identifiable assets at September 30, 2013 and 2012							$	4,661.90		$	3,835.00
	Risk Management
	Total revenues	$	149.7		$	142.2		$	459.5		$	426.9
	Earnings before income taxes	$	17.9		$	18.2		$	59.6		$	54.9
	Identifiable assets at September 30, 2013 and 2012							$	546.2		$	547.9
	Corporate
	Total revenues	$	139.8		$	28.5		$	278.3		$	81.7
	Loss before income taxes	$	(29.7	)	$	(23.9	)	$	(84.9	)	$	(58.8	)
	Identifiable assets at September 30, 2013 and 2012							$	762.1		$	626.4

Effect_of_New_Accounting_Prono1

Effect of New Accounting Pronouncements (Policies)	9 Months Ended
	Sep. 30, 2013
Accounting Changes And Error Corrections [Abstract]
Presentation of Unrecognized Tax Benefits	Presentation of Unrecognized Tax Benefits
	In July 2013, the Financial Accounting Standards Board (which we refer to as the FASB) issued ASU 2013-11, “Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists,” which provides explicit guidance on the presentation of certain unrecognized tax benefits in the financial statements that did not previously exist. The ASU provides that a liability related to an unrecognized tax benefit would be offset against a deferred tax asset for a net operating loss carryforward, a similar tax loss or a tax credit carryforward if such settlement is required or expected in the event the uncertain tax position is disallowed. In that case, the liability associated with the unrecognized tax benefit is presented in the financial statements as a reduction to the related deferred tax asset. In situations in which a net operating loss carryforward, a similar tax loss or a tax credit carryforward is not available at the reporting date under the tax law of the jurisdiction or the tax law of the jurisdiction does not require, and the entity does not intend to use, the deferred tax asset for such purpose, the unrecognized tax benefit will be presented in the financial statements as a liability and will not be combined with deferred tax assets. This new guidance is effective for annual and interim periods beginning after December 15, 2013. Early adoption is permitted. Management is currently evaluating whether or not to early adopt and the impact of the new guidance upon adoption, but believes that the impact on the financial statements will not be material.
Other Comprehensive Income	Other Comprehensive Income
	In February 2013, the FASB issued ASU 2013-02, Comprehensive Income (Topic 220), “Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income,” which requires significant items reclassified out of accumulated other comprehensive income (which we refer to as AOCI) to net income in their entirety in the same reporting period, to be reported to show the effect of the reclassifications on the respective line items of the statement where net income is presented. These reclassifications can be presented either on the face of the statement where net income is presented or in the notes to the financial statements. For items that are not reclassified to net income in their entirety in the same reporting period, a cross reference to other disclosures currently required under U.S. GAAP is required in the notes to the consolidated financial statements. The new guidance also requires companies to report changes in the accumulated balances of each component of AOCI. This new guidance was effective for annual and interim periods beginning after December 15, 2012. We adopted the new guidance effective January 1, 2013. The adoption affected the disclosures made in our unaudited consolidated financial statements and notes thereto, but did not have any impact on our results of operations or financial position.

Business_Combinations_Tables

Business Combinations (Tables)	9 Months Ended
	Sep. 30, 2013
Business Combinations [Abstract]
Acquisition Method for Recording Business Combinations	During the nine-month period ended September 30, 2013, we acquired substantially all of the net assets of the following firms in exchange for our common stock and/or cash. These acquisitions have been accounted for using the acquisition method for recording business combinations (in millions except share data):
	Name and Effective	Common		Common		Cash		Accrued		Escrow		Recorded		Total		Maximum
	Date of Acquisition	Shares		Share		Paid		Liability		Deposited		Earnout		Recorded		Potential
		Issued		Value								Payable		Purchase		Earnout
														Price		Payable
		(000s)
	Metzler Brothers Insurance February 1, 2013		—	$	—	$	3.4	$	—	$	0.4	$	0.7	$	4.5	$	1.4
	Advanced Benefit Advisors, Inc. (ABA) April 1, 2013		—		—		10.9		—		0.1		1.8		12.8		7
	Property & Commercial Limited (PCL) April 1, 2013		—		—		65.1		—		—		—		65.1		—
	Garza Long Group, LLC (GLG) May 1, 2013		—		—		4.3		—		0.1		0.5		4.9		6.7
	Bollinger, Inc. (BOL) August 1, 2013		3,177		140		155.1		—		22		—		317.1		—
	Dickinson & Associates, Inc. (DA) August 1, 2013		—		—		10.9		—		0.1		0.5		11.5		4.8
	Belmont International (BEL) September 1, 2013		—		—		21.7		—		2.5		2.8		27		3.2
	R.W. Scobie, Inc. (RWS) September 1, 2013		223		9.5		4.4		—		—		2.4		16.3		5
	Jeffrey Haber & Michael Fischman (HF) September 20, 2013		—		—		7		—		—		8.4		15.4		10.3
	Eight other acquisitions completed in 2013		30		1.4		8.4		—		0.4		6.4		16.6		8.7
			3,430	$	150.9	$	291.2	$	—	$	25.6	$	23.5	$	491.2	$	47.1
Summary of Estimated Fair Values of Net Assets Acquired	The following is a summary of the estimated fair values of the net assets acquired at the date of each acquisition made in the nine-month period ended September 30, 2013 (in millions):
		ABA		PCL		GLG		BOL		DA		BEL		RWS		HF		Nine		Total
																		Other
																		Acquisitions
	Cash	$	—	$	2.4	$	—	$	7.6	$	0.6	$	5.3	$	0.2	$	—	$	0.2	$	16.3
	Other current assets		—		32.9		—		39.4		—		19.1		8.2		—		0.2		99.8
	Fixed assets		—		2.7		—		3.1		—		0.4		0.4		—		0.2		6.8
	Noncurrent assets		—		0.4		—		2.2		—		—		—		—		—		2.6
	Goodwill		7.6		44.6		2.4		197		4		15.3		12.8		8.4		7.9		300
	Expiration lists		5		25.6		2.4		132.5		7.3		9		6.7		6.7		13.4		208.6
	Non-compete agreements		0.2		—		0.1		0.4		0.2		0.2		—		0.3		0.4		1.8
	Trade names		—		0.1		—		1.7		—		—		—		—		—		1.8
	Total assets acquired		12.8		108.7		4.9		383.9		12.1		49.3		28.3		15.4		22.3		637.7
	Current liabilities		—		35.5		—		50.9		0.6		20.5		9.4		—		0.7		117.6
	Noncurrent liabilities		—		8.1		—		15.9		—		1.8		2.6		—		0.5		28.9
	Total liabilities assumed		—		43.6		—		66.8		0.6		22.3		12		—		1.2		146.5
	Total net assets acquired	$	12.8	$	65.1	$	4.9	$	317.1	$	11.5	$	27	$	16.3	$	15.4	$	21.1	$	491.2
Summary of Unaudited Pro Forma Historical Results	The following is a summary of the unaudited pro forma historical results, as if these entities had been acquired at January 1, 2012 (in millions, except per share data):
		Three-month period ended				Nine-month period ended
		September 30,				September 30,
		2013		2012		2013		2012
	Total revenues	$	850.9	$	693.7	$	2,385.90	$	1,981.00
	Net earnings		75.2		63.5		216.2		168.7
	Basic net earnings per share		0.57		0.5		1.66		1.37
	Diluted net earnings per share		0.57		0.5		1.64		1.35

Intangible_Assets_Tables

Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2013
Goodwill And Intangible Assets Disclosure [Abstract]
Carrying Amount of Goodwill Allocated by Domestic and Foreign Operations	The carrying amount of goodwill at September 30, 2013 and December 31, 2012 allocated by domestic and foreign operations is as follows (in millions):
		Brokerage			Risk			Corporate		Total
					Management
	At September 30, 2013
	United States	$	1,398.60		$	19.3		$	—	$	1,417.90
	Foreign, principally Australia, Canada and the U.K.		351.6			2			—		353.6
	Total goodwill - net	$	1,750.20		$	21.3		$	—	$	1,771.50
	At December 31, 2012
	United States	$	1,158.10		$	19.2		$	—	$	1,177.30
	Foreign, principally Australia, Canada and the U.K.		293.3			2.1			—		295.4
	Total goodwill - net	$	1,451.40		$	21.3		$	—	$	1,472.70
Changes in Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for the nine-month period ended September 30, 2013 are as follows (in millions):
					Risk
		Brokerage			Management			Corporate		Total
	Balance as of December 31, 2012	$	1,451.40		$	21.3		$	—	$	1,472.70
	Goodwill acquired during the period		300			—			—		300
	Goodwill adjustments due to appraisals and other acquisition adjustments		3.3			—			—		3.3
	Foreign currency translation adjustments during the period		(4.5	)		—			—		(4.5	)
	Balance as of September 30, 2013	$	1,750.20		$	21.3		$	—	$	1,771.50
Major Classes of Amortizable Intangible Assets	Major classes of amortizable intangible assets at September 30, 2013 and December 31, 2012 consist of the following (in millions):
		September 30,			December 31,
		2013			2012
	Expiration lists	$	1,372.40		$	1,175.00
	Accumulated amortization - expiration lists		(477.1	)		(390.8	)
			895.3			784.2
	Non-compete agreements		31.8			30.9
	Accumulated amortization - non-compete agreements		(25.0	)		(23.3	)
			6.8			7.6
	Trade names		22.4			23
	Accumulated amortization - trade names		(6.5	)		(5.2	)
			15.9			17.8
	Net amortizable assets	$	918		$	809.6
Estimated Aggregate Amortization Expense	Estimated aggregate amortization expense for each of the next five years is as follows:
	2013 (remaining three months)	$	32.6
	2014		128.5
	2015		123.4
	2016		117.9
	2017		109.8
	Total	$	512.2

Credit_and_Other_Debt_Agreemen1

Credit and Other Debt Agreements (Tables)	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]
Summary of Debt	The following is a summary of our corporate debt (in millions):
		September 30,		December 31,
		2013		2012
	Note Purchase Agreements:
	Semi-annual payments of interest, fixed rate of 6.26%, balloon due 2014	$	100	$	100
	Semi-annual payments of interest, fixed rate of 6.44%, balloon due 2017		300		300
	Semi-annual payments of interest, fixed rate of 5.85%, $50 million due in 2016, 2018 and 2019		150		150
	Semi-annual payments of interest, fixed rate of 5.18%, balloon due 2021		75		75
	Semi-annual payments of interest, fixed rate of 5.49%, balloon due 2023		50		50
	Semi-annual payments of interest, fixed rate of 3.99%, balloon due 2020		50		50
	Semi-annual payments of interest, fixed rate of 3.69%, balloon due 2022		200		—
	Total Note Purchase Agreements		925		725
	Credit Agreement:
	Periodic payments of interest and principal, prime or LIBOR plus up to 1.45%, expires September 19, 2018		135.5		129
		$	1,060.50	$	854

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net EPS	The following table sets forth the computation of basic and diluted net earnings per share (in millions, except per share data):
		Three-month period ended				Nine-month period ended
		September  30,				September  30,
		2013		2012		2013		2012
	Net earnings	$	74.6	$	61.7	$	208.6	$	161.5
	Weighted average number of common shares outstanding		129.8		123.1		127.7		119.7
	Dilutive effect of stock options using the treasury stock method		1.5		1.4		1.6		1.5
	Weighted average number of common and common equivalent shares outstanding		131.3		124.5		129.3		121.2
	Basic net earnings per share	$	0.57	$	0.5	$	1.63	$	1.35
	Diluted net earnings per share	$	0.57	$	0.5	$	1.61	$	1.33

Stock_Option_Plans_Tables

Stock Option Plans (Tables)	9 Months Ended
	Sep. 30, 2013
Text Block [Abstract]
Black-Scholes Option Pricing Model with Weighted Average	For purposes of expense recognition, the estimated fair values of the stock option grants are amortized to expense over the options’ vesting period. We estimated the fair value of stock options at the date of grant using the Black-Scholes option pricing model with the following weighted average assumptions:
		2013				2012
	Expected dividend yield		3.5	%			4	%
	Expected risk-free interest rate		1.2	%			1.2	%
	Volatility		29.6	%			26.7	%
	Expected life (in years)		6				5
Stock Option Activity and Related Information	The following is a summary of our stock option activity and related information for 2013 (in millions, except exercise price and year data):
		Nine-month period ended September 30, 2013
										Weighted
										Average
						Weighted				Remaining
		Shares				Average				Contractual				Aggregate
		Under				Exercise				Term				Intrinsic
		Option				Price				(in years)				Value
	Beginning balance		9			$	28.8
	Granted		1.6				39.17
	Exercised		(2.1	)			27
	Forfeited or canceled		—				—
	Ending balance		8.5			$	31.29				3.83			$	105
	Exercisable at end of period		3.9			$	27.67				2.38			$	62.9
	Ending vested and expected to vest		8.4			$	31.2				3.8			$	104.2
Other Information Regarding Stock Options Outstanding and Exercisable	Other information regarding stock options outstanding and exercisable at September 30, 2013 is summarized as follows (in millions, except exercise price and year data):
				Options Outstanding												Options Exercisable
	Range of Exercise Prices			Number				Weighted				Weighted				Number		Weighted
				Outstanding				Average				Average				Exercisable		Average
								Remaining				Exercise						Exercise
								Contractual				Price						Price
								Term
								(in years)
	$ 10.58 - $ 27.25				2.9				2.78			$	25.87				2.1	$	25.88
	27.35 - 30.95				2.4				2.56				29.73				1.7		29.44
	31.24 - 35.71				1.5				4.92				35.4				0.1		32.95
	35.95 - 35.95				—				5.84				35.95				—		—
	39.17 - 39.17				1.7				6.45				39.17				—		—
	$ 10.58 - $ 39.17				8.5				3.83			$	31.29				3.9	$	27.67

Retirement_Plans_Tables

Retirement Plans (Tables)	9 Months Ended
	Sep. 30, 2013
Compensation And Retirement Disclosure [Abstract]
Components of Net Periodic Pension Benefit Cost	The components of the net periodic pension benefit cost for the plan consists of the following (in millions):
		Three-month period ended						Nine-month period ended
		September 30,						September 30,
		2013			2012			2013			2012
	Service cost	$	0.2		$	0.1		$	0.4		$	0.3
	Interest cost on benefit obligation		2.9			3			8.8			9
	Expected return on plan assets		(4.2	)		(3.8	)		(12.8	)		(11.4	)
	Amortization of net actuarial loss		2			1.8			5.9			5.4
	Net periodic benefit cost	$	0.9		$	1.1		$	2.3		$	3.3

Investments_Tables

Investments (Tables)	9 Months Ended
	Sep. 30, 2013
Equity Method Investments And Joint Ventures [Abstract]
Investments Reported in Other Current and Non-Current Assets	The following is a summary of our investments and the related funding commitments (in millions):
		30-Sep-13				December 31,
				Funding		2012
		Assets		Commitments		Assets
	Chem-Mod LLC	$	4	$	—	$	4
	Chem-Mod International LLC		2		—		2
	C-Quest Technology LLC		2		—		—
	Clean-coal investments
	Non-controlling interest in four limited liability companies that own nine 2009 Era Clean Coal Plants		8.2		1.8		2.8
	Controlling interest in two limited liability companies that own five 2009 Era Clean Coal Plants		6.8		0.9		6.3
	Non-controlling interest in six limited liability companies that own five 2011 Era Clean Coal Plants		12.1		—		13.2
	Controlling interest in five limited liability companies that own nine 2011 Era Clean Coal Plants		41.4		2.2		9.2
	Controlling interest in a limited liability company that owns six 2011 Era Clean Coal Plants		7.4		0.7		5.1
	Notes receivable and interest from co-investor related to the sales of three 2009 Era Plants		—		—		8.5
	Other investments		3.6		5		3
	Total investments	$	87.5	$	10.6	$	54.1

Commitments_Contingencies_and_1

Commitments, Contingencies and Off-Balance Sheet Arrangements (Tables)	9 Months Ended
	Sep. 30, 2013
Commitments And Contingencies Disclosure [Abstract]
Contractual Obligations	Our future minimum cash payments, including interest, associated with our contractual obligations pursuant to the note purchase agreements and Credit Agreement, operating leases and purchase commitments at September 30, 2013 were as follows (in millions):
		Payments Due by Period
	Contractual Obligations	2013			2014			2015			2016			2017		Thereafter		Total
	Note purchase agreements	$	—		$	100		$	—		$	50		$	300	$	475	$	925
	Credit Agreement		135.5			—			—			—			—		—		135.5
	Interest on debt		8.1			50.4			44.1			44.1			41.2		76.6		264.5
	Total debt obligations		143.6			150.4			44.1			94.1			341.2		551.6		1,325.00
	Operating lease obligations		18.8			69.4			61.8			50.6			40.2		109.3		350.1
	Less sublease arrangements		(2.1	)		(1.8	)		(0.8	)		(0.1	)		—		—		(4.8	)
	Outstanding purchase obligations		4.1			9.4			7			1.3			0.3		—		22.1
	Total contractual obligations	$	164.4		$	227.4		$	112.1		$	145.9		$	381.7	$	660.9	$	1,692.40
Off-Balance Sheet Commitments	Off-Balance Sheet Commitments - Our total unrecorded commitments associated with outstanding letters of credit, financial guarantees and funding commitments as of September 30, 2013 were as follows (in millions):
																		Total
		Amount of Commitment Expiration by Period																Amounts
	Off-Balance Sheet Commitments	2013			2014			2015			2016			2017		Thereafter		Committed
	Letters of credit	$	—		$	—		$	—		$	—		$	—	$	15.2	$	15.2
	Financial guarantees		—			—			—			—			—		9.3		9.3
	Funding commitments		7			0.7			—			—			—		2.9		10.6
	Total commitments	$	7		$	0.7		$	—		$	—		$	—	$	27.4	$	35.1

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]
Schedule of Accumulated Comprehensive Loss	The after-tax components of our accumulated other comprehensive loss consist of the following:
		Pension			Foreign			Fair Value of			Accumulated
		Liability			Currency			Derivative			Comprehensive
					Translation			Investments			Loss
	Balance as of December 31, 2012	$	(52.4	)	$	20.5		$	(0.9	)	$	(32.8	)
	Net change in period		0.4			(9.9	)		0.5			(9.0	)
	Balance as of September 30, 2013	$	(52.0	)	$	10.6		$	(0.4	)	$	(41.8	)

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]
Schedule of Segment Reporting Information by Segment	Financial information relating to our segments for the three-month and nine-month periods ended September 30, 2013 and 2012 is as follows (in millions):
		Three-month period						Nine-month period
		ended September 30,						ended September 30,
		2013			2012			2013			2012
	Brokerage
	Total revenues	$	546.3		$	479.7		$	1,551.60		$	1,338.50
	Earnings before income taxes	$	97.3		$	82		$	250.5		$	203.8
	Identifiable assets at September 30, 2013 and 2012							$	4,661.90		$	3,835.00
	Risk Management
	Total revenues	$	149.7		$	142.2		$	459.5		$	426.9
	Earnings before income taxes	$	17.9		$	18.2		$	59.6		$	54.9
	Identifiable assets at September 30, 2013 and 2012							$	546.2		$	547.9
	Corporate
	Total revenues	$	139.8		$	28.5		$	278.3		$	81.7
	Loss before income taxes	$	(29.7	)	$	(23.9	)	$	(84.9	)	$	(58.8	)
	Identifiable assets at September 30, 2013 and 2012							$	762.1		$	626.4

Nature_of_Operations_and_Basis1

Nature of Operations and Basis of Presentation - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
	Segment
	Country
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of countries in which the company has operations	20
Number of countries in which the company does business through a network of correspondent brokers and consultants	140
Number of reportable segments	3

Business_Combinations_Acquisit

Business Combinations - Acquisition Method for Recording Business Combinations (Detail) (USD $)	9 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Sep. 30, 2013
Business Acquisition [Line Items]
Common Shares Issued	3,430
Common Share Value	$150.90
Cash Paid	291.2
Accrued Liability
Escrow Deposited	25.6
Recorded Earnout Payable	23.5
Total Recorded Purchase Price	491.2
Maximum Potential Earnout Payable	47.1
Metzler Brothers Insurance [Member]
Business Acquisition [Line Items]
Common Shares Issued
Common Share Value
Cash Paid	3.4
Accrued Liability
Escrow Deposited	0.4
Recorded Earnout Payable	0.7
Total Recorded Purchase Price	4.5
Maximum Potential Earnout Payable	1.4
Advanced Benefit Advisors, Inc. (ABA) [Member]
Business Acquisition [Line Items]
Common Shares Issued
Common Share Value
Cash Paid	10.9
Accrued Liability
Escrow Deposited	0.1
Recorded Earnout Payable	1.8
Total Recorded Purchase Price	12.8
Maximum Potential Earnout Payable	7
Property & Commercial Limited (PCL) [Member]
Business Acquisition [Line Items]
Common Shares Issued
Common Share Value
Cash Paid	65.1
Accrued Liability
Escrow Deposited
Recorded Earnout Payable
Total Recorded Purchase Price	65.1
Maximum Potential Earnout Payable
Garza Long Group, LLC (GLG) [Member]
Business Acquisition [Line Items]
Common Shares Issued
Common Share Value
Cash Paid	4.3
Accrued Liability
Escrow Deposited	0.1
Recorded Earnout Payable	0.5
Total Recorded Purchase Price	4.9
Maximum Potential Earnout Payable	6.7
Bollinger, Inc. (BOL) [Member]
Business Acquisition [Line Items]
Common Shares Issued	3,177
Common Share Value	140
Cash Paid	155.1
Accrued Liability
Escrow Deposited	22
Recorded Earnout Payable
Total Recorded Purchase Price	317.1
Maximum Potential Earnout Payable
Dickinson & Associates, Inc. (DA) [Member]
Business Acquisition [Line Items]
Common Shares Issued
Common Share Value
Cash Paid	10.9
Accrued Liability
Escrow Deposited	0.1
Recorded Earnout Payable	0.5
Total Recorded Purchase Price	11.5
Maximum Potential Earnout Payable	4.8
Belmont International (BEL) [Member]
Business Acquisition [Line Items]
Common Shares Issued
Common Share Value
Cash Paid	21.7
Accrued Liability
Escrow Deposited	2.5
Recorded Earnout Payable	2.8
Total Recorded Purchase Price	27
Maximum Potential Earnout Payable	3.2
R.W. Scobie, Inc. (RWS) [Member]
Business Acquisition [Line Items]
Common Shares Issued	223
Common Share Value	9.5
Cash Paid	4.4
Accrued Liability
Escrow Deposited
Recorded Earnout Payable	2.4
Total Recorded Purchase Price	16.3
Maximum Potential Earnout Payable	5
Jeffrey Haber & Michael Fischman (HF) [Member]
Business Acquisition [Line Items]
Common Shares Issued
Common Share Value
Cash Paid	7
Accrued Liability
Escrow Deposited
Recorded Earnout Payable	8.4
Total Recorded Purchase Price	15.4
Maximum Potential Earnout Payable	10.3
Eight Other Acquisitions Completed [Member]
Business Acquisition [Line Items]
Common Shares Issued	30
Common Share Value	1.4
Cash Paid	8.4
Accrued Liability
Escrow Deposited	0.4
Recorded Earnout Payable	6.4
Total Recorded Purchase Price	16.6
Maximum Potential Earnout Payable	$8.70

Business_Combinations_Acquisit1

Business Combinations - Acquisition Method for Recording Business Combinations (Parenthetical) (Detail)	9 Months Ended
	Sep. 30, 2013
Metzler Brothers Insurance [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	1-Feb-13
Advanced Benefit Advisors, Inc. (ABA) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	1-Apr-13
Property & Commercial Limited (PCL) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	1-Apr-13
Garza Long Group, LLC (GLG) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	1-May-13
Bollinger, Inc. (BOL) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	1-Aug-13
Dickinson & Associates, Inc. (DA) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	1-Aug-13
Belmont International (BEL) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	1-Sep-13
R.W. Scobie, Inc. (RWS) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	1-Sep-13
Jeffrey Haber & Michael Fischman (HF) [Member]
Business Acquisition [Line Items]
Effective Date of Acquisition	1-Sep-13

Business_Combinations_Addition

Business Combinations - Additional Information (Detail)

3 Months Ended

9 Months Ended

141 Months Ended

3 Months Ended

9 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

In Millions, except Share data in Thousands, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Brokerage [Member]

Brokerage [Member]

Brokerage [Member]

Acquisitions Made Prior to 2009 [Member]

2013 Acquisitions [Member]

2013 Acquisitions [Member]

2013 Acquisitions [Member]

2013 Acquisitions [Member]

2013 Acquisitions [Member]

2013 Acquisitions [Member]

2013 Acquisitions [Member]

2013 Acquisitions [Member]

2013 Acquisitions [Member]

2012 Acquisitions [Member]

2012 Acquisitions [Member]

Giles Group Of Companies [Member]

Giles Group Of Companies [Member]

Giles Group Of Companies [Member]

Entity

Entity

Entity

Entity

Entity

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

Brokerage [Member]

Brokerage [Member]

Brokerage [Member]

Brokerage [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

USD ($)

GBP (£)

USD ($)

Entity

USD ($)

Expiration Lists [Member]

Non-Compete Agreements [Member]

Trade Names [Member]

Market Approach Valuation Technique [Member]

Income Approach Valuation Technique [Member]

Market Approach Valuation Technique [Member]

Income Approach Valuation Technique [Member]

Income Approach Valuation Technique [Member]

Income Approach Valuation Technique [Member]

Office

USD ($)

USD ($)

USD ($)

Employees

Business Acquisition [Line Items]

Cash paid for acquisition of equity interest

$291.20

$3.40

$370

£ 233

Number of employees at offices of acquired entity

1,100,000,000

1,100,000,000

Number of offices in which acquiree entity operates

43,000,000

43,000,000

Unrealized fair value, pretax gain

5

Revenue growth rate

5.00%

2.00%

10.00%

10.00%

2.00%

10.00%

Discount rate

8.00%

10.50%

8.50%

14.00%

10.50%

14.00%

Accretion of the discount on acquisition

2.9

2.4

Income related to net adjustments

3.3

1.3

7.2

6

Expense related to accretion of the discount recorded

8.7

7

Number of companies acquired

20

12

53

31

265

4

Aggregate amount of maximum earnout obligations related to acquisitions

400.4

Aggregate amount of maximum earnout obligations related to acquisitions, recorded in consolidated balance sheet

140.4

Goodwill

300

300

300

300

Expiration lists

208.6

208.6

208.6

208.6

208.6

Non-compete agreements

1.8

1.8

1.8

1.9

1.8

Trade names

1.8

1.8

1.8

1.8

1.8

Attrition rate

5.00%

15.00%

5.00%

15.00%

Expiration lists, amortization period, minimum, years

3 years

Expiration lists, amortization period, maximum, years

15 years

Non-compete agreements, amortization period, minimum, years

3 years

Non-compete agreements, amortization period, maximum, years

5 years

Trade names, amortization period, minimum ,years

5 years

Trade names, amortization period, maximum, years

10 years

Amortization of intangible assets related to brokerage segment

0.3

2.2

3.4

Business acquisition not deductible for income tax purposes

174.9

0.7

1.8

Deferred tax liability

23.4

Goodwill related to nondeductible amortizable intangible assets

23.4

Common stock issued related to acquisition, shares

3,430

425

Current goodwill related to earnout obligations

0.1

Annualized revenue of business acquisitions during 6 month period ended June 30, 2013

176.4

Total revenues related to 2013 acquisitions in the aggregate

850.9

693.7

2,385.90

1,981

41.5

Net earnings

$75.20

$63.50

$216.20

$168.70

$4.30

Business_Combinations_Summary_

Business Combinations - Summary of Estimated Fair Values of Net Assets Acquired (Detail) (USD $)	Sep. 30, 2013
In Millions, unless otherwise specified
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash	$16.30
Other current assets	99.8
Fixed assets	6.8
Noncurrent assets	2.6
Goodwill	300
Expiration lists	208.6
Non-compete agreements	1.8
Trade names	1.8
Total assets acquired	637.7
Current liabilities	117.6
Noncurrent liabilities	28.9
Total liabilities assumed	146.5
Total net assets acquired	491.2
Advanced Benefit Advisors, Inc. (ABA) [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash
Other current assets
Fixed assets
Noncurrent assets
Goodwill	7.6
Expiration lists	5
Non-compete agreements	0.2
Trade names
Total assets acquired	12.8
Current liabilities
Noncurrent liabilities
Total liabilities assumed
Total net assets acquired	12.8
Property & Commercial Limited (PCL) [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash	2.4
Other current assets	32.9
Fixed assets	2.7
Noncurrent assets	0.4
Goodwill	44.6
Expiration lists	25.6
Trade names	0.1
Total assets acquired	108.7
Current liabilities	35.5
Noncurrent liabilities	8.1
Total liabilities assumed	43.6
Total net assets acquired	65.1
Garza Long Group, LLC (GLG) [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash
Other current assets
Fixed assets
Noncurrent assets
Goodwill	2.4
Expiration lists	2.4
Non-compete agreements	0.1
Trade names
Total assets acquired	4.9
Current liabilities
Noncurrent liabilities
Total liabilities assumed
Total net assets acquired	4.9
Bollinger, Inc. (BOL) [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash	7.6
Other current assets	39.4
Fixed assets	3.1
Noncurrent assets	2.2
Goodwill	197
Expiration lists	132.5
Non-compete agreements	0.4
Trade names	1.7
Total assets acquired	383.9
Current liabilities	50.9
Noncurrent liabilities	15.9
Total liabilities assumed	66.8
Total net assets acquired	317.1
Dickinson & Associates, Inc. (DA) [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash	0.6
Other current assets
Fixed assets
Noncurrent assets
Goodwill	4
Expiration lists	7.3
Non-compete agreements	0.2
Trade names
Total assets acquired	12.1
Current liabilities	0.6
Noncurrent liabilities
Total liabilities assumed	0.6
Total net assets acquired	11.5
Belmont International (BEL) [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash	5.3
Other current assets	19.1
Fixed assets	0.4
Noncurrent assets
Goodwill	15.3
Expiration lists	9
Non-compete agreements	0.2
Trade names
Total assets acquired	49.3
Current liabilities	20.5
Noncurrent liabilities	1.8
Total liabilities assumed	22.3
Total net assets acquired	27
R.W. Scobie, Inc. (RWS) [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash	0.2
Other current assets	8.2
Fixed assets	0.4
Noncurrent assets
Goodwill	12.8
Expiration lists	6.7
Trade names
Total assets acquired	28.3
Current liabilities	9.4
Noncurrent liabilities	2.6
Total liabilities assumed	12
Total net assets acquired	16.3
Jeffrey Haber & Michael Fischman (HF) [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash
Other current assets
Fixed assets
Noncurrent assets
Goodwill	8.4
Expiration lists	6.7
Non-compete agreements	0.3
Trade names
Total assets acquired	15.4
Current liabilities
Noncurrent liabilities
Total liabilities assumed
Total net assets acquired	15.4
Nine Other Acquisitions Completed [Member]
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Cash	0.2
Other current assets	0.2
Fixed assets	0.2
Noncurrent assets
Goodwill	7.9
Expiration lists	13.4
Non-compete agreements	0.4
Trade names
Total assets acquired	22.3
Current liabilities	0.7
Noncurrent liabilities	0.5
Total liabilities assumed	1.2
Total net assets acquired	$21.10

Business_Combinations_Summary_1

Business Combinations - Summary of Unaudited Pro Forma Historical Results (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Business Combinations [Abstract]
Total revenues	$850.90	$693.70	$2,385.90	$1,981
Net earnings	$75.20	$63.50	$216.20	$168.70
Basic net earnings per share	$0.57	$0.50	$1.66	$1.37
Diluted net earnings per share	$0.57	$0.50	$1.64	$1.35

Intangible_Assets_Carrying_Amo

Intangible Assets - Carrying Amount of Goodwill Allocated by Domestic and Foreign Operations (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Goodwill [Line Items]
Total goodwill-net	$1,771.50	$1,472.70
United States [Member]
Goodwill [Line Items]
Total goodwill-net	1,417.90	1,177.30
Foreign, principally Australia, Canada and the U.K. [Member]
Goodwill [Line Items]
Total goodwill-net	353.6	295.4
Brokerage [Member]
Goodwill [Line Items]
Total goodwill-net	1,750.20	1,451.40
Brokerage [Member] | United States [Member]
Goodwill [Line Items]
Total goodwill-net	1,398.60	1,158.10
Brokerage [Member] | Foreign, principally Australia, Canada and the U.K. [Member]
Goodwill [Line Items]
Total goodwill-net	351.6	293.3
Risk Management [Member]
Goodwill [Line Items]
Total goodwill-net	21.3	21.3
Risk Management [Member] | United States [Member]
Goodwill [Line Items]
Total goodwill-net	19.3	19.2
Risk Management [Member] | Foreign, principally Australia, Canada and the U.K. [Member]
Goodwill [Line Items]
Total goodwill-net	2	2.1
Corporate [Member]
Goodwill [Line Items]
Total goodwill-net
Corporate [Member] | United States [Member]
Goodwill [Line Items]
Total goodwill-net
Corporate [Member] | Foreign, principally Australia, Canada and the U.K. [Member]
Goodwill [Line Items]
Total goodwill-net

Intangible_Assets_Changes_in_C

Intangible Assets - Changes in Carrying Amount of Goodwill (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Goodwill [Line Items]
Beginning Balance	$1,472.70
Goodwill acquired during the period	300
Goodwill adjustments due to appraisals and other acquisition adjustments	3.3
Foreign currency translation adjustments during the period	-4.5
Ending Balance	1,771.50
Brokerage [Member]
Goodwill [Line Items]
Beginning Balance	1,451.40
Goodwill acquired during the period	300
Goodwill adjustments due to appraisals and other acquisition adjustments	3.3
Foreign currency translation adjustments during the period	-4.5
Ending Balance	1,750.20
Risk Management [Member]
Goodwill [Line Items]
Beginning Balance	21.3
Goodwill acquired during the period
Goodwill adjustments due to appraisals and other acquisition adjustments
Foreign currency translation adjustments during the period
Ending Balance	21.3
Corporate [Member]
Goodwill [Line Items]
Beginning Balance
Goodwill acquired during the period
Goodwill adjustments due to appraisals and other acquisition adjustments
Foreign currency translation adjustments during the period
Ending Balance

Intangible_Assets_Major_Classe

Intangible Assets - Major Classes of Amortizable Intangible Assets (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, net	$918	$809.60
Expiration Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	1,372.40	1,175
Accumulated amortization	-477.1	-390.8
Amortizable intangible assets, net	895.3	784.2
Non-Compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	31.8	30.9
Accumulated amortization	-25	-23.3
Amortizable intangible assets, net	6.8	7.6
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross	22.4	23
Accumulated amortization	-6.5	-5.2
Amortizable intangible assets, net	$15.90	$17.80

Intangible_Assets_Estimated_Ag

Intangible Assets - Estimated Aggregate Amortization Expense (Detail) (USD $)	Sep. 30, 2013
In Millions, unless otherwise specified
Goodwill And Intangible Assets Disclosure [Abstract]
2013 (remaining three months)	$32.60
2014	128.5
2015	123.4
2016	117.9
2017	109.8
Total	$512.20

Credit_and_Other_Debt_Agreemen2

Credit and Other Debt Agreements - Additional information (Detail) (USD $)

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 19, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Note Purchase Agreements [Member]

Note Purchase Agreements [Member]

Note Purchase Agreements [Member]

Note Purchase Agreements [Member]

Note Purchase Agreements [Member]

Note Purchase Agreements [Member]

Note Purchase Agreements [Member]

Note Purchase Agreements [Member]

Note Purchase Agreements [Member]

Note Purchase Agreements [Member]

Note Purchase Agreements [Member]

Note Purchase Agreements [Member]

Credit Agreement [Member]

Credit Agreement [Member]

Credit Agreement [Member]

Credit Agreement [Member]

Previous Credit Facility [Member]

Level 3 [Member]

Senior Note, Series A [Member]

Senior Note, Series B [Member]

Senior Note, Series C [Member]

Senior Note, Series C [Member]

Senior Note, Series C [Member]

Senior Note, Series C [Member]

Senior Note, Series D [Member]

Senior Note, Series E [Member]

3.99% Senior Notes, Series F [Member]

Private Placement [Member]

Institution

Standby Letters of Credit [Member]

Swing Loan [Member]

First Installment [Member]

Second Installment [Member]

Third Installment [Member]

3.69% Senior Notes Series G [Member]

Debt Instrument [Line Items]

Notes issued and sold

$100,000,000

$300,000,000

$150,000,000

$75,000,000

$50,000,000

$50,000,000

Note payable, semi-annual payments of interest, fixed rate

6.26%

6.44%

5.85%

5.18%

5.49%

3.99%

Debt instrument, maturity date

3-Aug-14

3-Aug-17

30-Nov-16

30-Nov-18

30-Nov-19

10-Feb-21

10-Feb-23

10-Jul-20

14-Jun-22

19-Sep-18

Private placement debt, additional amount committed to borrow

200,000,000

Interest rate

3.69%

Amount payable to redeem the notes, percent of the principal amount

100.00%

Discount rate used to compute the remaining scheduled payments of principal and interest

U.S. Treasury yields plus 0.5%

Line of credit facility, maximum borrowing capacity

600,000,000

600,000,000

500,000,000

Number of financial institutions entered in unsecured multicurrency credit agreement

15

Early termination fees incurred on termination of credit facility

0

Long-term debt, gross

75,000,000

50,000,000

Line of credit facility, maximum amount outstanding during period

850,000,000

Fixed rate (alternative one) over LIBOR

0.85%

Fixed rate (alternative two) over LIBOR

0.95%

Fixed rate (alternative three) over LIBOR

1.05%

Fixed rate (alternative four) over LIBOR

1.25%

Fixed rate (alternative five) over LIBOR

1.45%

Annual facility fee of revolving credit facility (alternative one)

0.15%

Annual facility fee of revolving credit facility (alternative two)

0.18%

Annual facility fee of revolving credit facility (alternative three)

0.20%

Annual facility fee of revolving credit facility (alternative four)

0.25%

Annual facility fee of revolving credit facility (alternative five)

0.30%

Debt acquisition costs

2,100,000

Line of credit facility, amount outstanding

15,200,000

Liabilities

4,038,000,000

3,693,700,000

8,700,000

Line of credit facility, fair value of amount outstanding

985,200,000

135,500,000

Line of credit facility, remaining borrowing capacity

449,300,000

Line of credit facility, increase in additional borrowings

445,500,000

162,000,000

59,800,000

Long-term debt

$925,000,000

Credit_and_Other_Debt_Agreemen3

Credit and Other Debt Agreements - Summary of Debt (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Debt Instrument [Line Items]
Semi-annual payments of interest	$1,060.50	$854
Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	925	725
Fixed Rate of 6.26%, Balloon Due 2014 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	100	100
Fixed Rate of 6.44%, Balloon Due 2017 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	300	300
Fixed Rate of 5.85%, $50.0 Million Due in 2016, 2018 and 2019 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	150	150
Fixed Rate of 5.18%, Balloon Due 2021 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	75	75
Fixed Rate of 5.49%, Balloon Due 2023 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	50	50
Fixed Rate of 3.99%, Balloon Due 2020 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	50	50
Fixed rate of 3.69%, balloon due 2022 [Member] | Note Purchase Agreements [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	200
Prime or LIBOR plus up to 1.45%, expires September 19, 2018 [Member] | Credit Agreement [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest	$135.50	$129

Credit_and_Other_Debt_Agreemen4

Credit and Other Debt Agreements - Summary of Debt (Parenthetical) (Detail) (USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fixed Rate of 6.26%, Balloon Due 2014 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	6.26%	6.26%
Principal payments, year due	2014	2014
Fixed Rate of 6.44%, Balloon Due 2017 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	6.44%	6.44%
Principal payments, year due	2017	2017
Fixed Rate of 5.85%, $50.0 Million Due in 2016, 2018 and 2019 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	5.85%	5.85%
Long-Term debt maturities repayments in 2016	50	50
Long-Term debt maturities repayments in 2018	50	50
Long-Term debt maturities repayments in 2019	50	50
Fixed Rate of 5.18%, Balloon Due 2021 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	5.18%	5.18%
Principal payments, year due	2021	2021
Fixed Rate of 5.49%, Balloon Due 2023 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	5.49%	5.49%
Principal payments, year due	2023	2023
Fixed Rate of 3.99%, Balloon Due 2020 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	3.99%	3.99%
Principal payments, year due	2020	2020
Fixed rate of 3.69%, balloon due 2022 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	3.69%	3.69%
Principal payments, year due	2022	2022
First Installment [Member] | Fixed Rate of 5.85%, $50.0 Million Due in 2016, 2018 and 2019 [Member]
Debt Instrument [Line Items]
Principal payments, year due	2016	2016
Second Installment [Member] | Fixed Rate of 5.85%, $50.0 Million Due in 2016, 2018 and 2019 [Member]
Debt Instrument [Line Items]
Principal payments, year due	2018	2018
Third Installment [Member] | Fixed Rate of 5.85%, $50.0 Million Due in 2016, 2018 and 2019 [Member]
Debt Instrument [Line Items]
Principal payments, year due	2019	2019
Credit Agreement [Member] | Prime or LIBOR plus up to 1.45%, expires September 19, 2018 [Member]
Debt Instrument [Line Items]
Semi-annual payments of interest, fixed rate	1.45%	1.45%
Periodic payments of interest and principal, expiry date	19-Sep-18	19-Sep-18

Earnings_Per_Share_Computation

Earnings Per Share - Computation of Basic and Diluted Net EPS (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Net earnings	$74.60	$61.70	$208.60	$161.50
Weighted average number of common shares outstanding	129.8	123.1	127.7	119.7
Dilutive effect of stock options using the treasury stock method	1.5	1.4	1.6	1.5
Weighted average number of common and common equivalent shares outstanding	131.3	124.5	129.3	121.2
Basic net earnings per share	$0.57	$0.50	$1.63	$1.35
Diluted net earnings per share	$0.57	$0.50	$1.61	$1.33

Earnings_Per_Share_Additional_

Earnings Per Share - Additional information (Detail)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Options to purchase common stock shares outstanding	1.7	1.4	1.2	1

Stock_Option_Plans_Additional_

Stock Option Plans - Additional information (Detail) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Mar. 13, 2013

Mar. 13, 2013

Mar. 16, 2012

Mar. 13, 2013

Long Term Incentive Plan [Member]

Performance-Based Restricted Stock [Member]

Black-Scholes Option Pricing Model [Member]

Black-Scholes Option Pricing Model [Member]

Minimum [Member]

Officer and Key Employees [Member]

Officer and Key Employees [Member]

Executive Officer [Member]

Y

Stock Option Plans [Line Items]

Maximum number of shares available

500,000

Maximum number of shares granted during any fiscal year to any person

200,000

100,000

Maximum amount payable for the shares granted during any fiscal year to any person

$3,000,000

Maximum period for the exercise of stock options, years

7 years

Minimum exercise price of stock options, percent of fair market value of a share of common stock on the date of grant

100.00%

Shares available for grant

8,000,000

1,665,000

1,355,000

Stock options granted, exercise percentage, year one

34.00%

34.00%

Stock options granted, exercise percentage, year two

33.00%

33.00%

Stock options granted, exercise percentage, year three

33.00%

33.00%

Number of years options expire, maximum

7 years

7 years

Minimum age of employee with not subject to award forfeiture on condition compliance

55

Period of Service from Grant Date Stock Options Awarded Not Subject to Forfeiture

2 years

Compensation expense related to stock option grants

2,200,000

2,200,000

5,400,000

5,200,000

Weighted average fair value per option for all options

$7.51

$5.49

Total intrinsic value of options exercised

28,800,000

19,100,000

28,800,000

19,100,000

Total unrecognized compensation cost related to nonvested options

$23,000,000

$23,000,000

Weighted average period, years

4 years

Stock_Option_Plans_BlackSchole

Stock Option Plans - Black-Scholes Option Pricing Model with Weighted Average (Detail)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]
Expected dividend yield	3.50%	4.00%
Expected risk-free interest rate	1.20%	1.20%
Volatility	29.60%	26.70%
Expected life (in years)	6 years	5 years

Stock_Option_Plans_Stock_Optio

Stock Option Plans - Stock Option Activity and Related Information (Detail) (USD $)	9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Under Option, Beginning balance	9
Shares Under Option, Granted	1.6
Shares Under Option, Exercised	-2.1
Shares Under Option, Forfeited or canceled
Shares Under Option, Ending balance	8.5
Shares Under Option, Exercisable at end of period	3.9
Shares Under Option, Ending vested and expected to vest	8.4
Weighted Average Exercise Price, Beginning balance	$28.80
Weighted Average Exercise Price, Granted	$39.17
Weighted Average Exercise Price, Exercised	$27
Weighted Average Exercise Price, Forfeited or canceled
Weighted Average Exercised Price, Ending balance	$31.29
Weighted Average Exercise Price, Exercisable at end of period	$27.67
Weighted Average Exercise price, Ending vested and expected to vest	$31.20
Weighted Average Remaining Contractual Term (in years), Ending balance	3 years 9 months 29 days
Weighted Average Remaining Contractual Term (in years), Exercisable at end of period	2 years 4 months 17 days
Weighted Average Remaining Contractual Term (in years), Ending vested and expected to vested	3 years 9 months 18 days
Aggregate Intrinsic Value, Ending Balance	$105
Aggregate Intrinsic Value, Exercisable at end of period	62.9
Aggregate Intrinsic Value, Ending vested and expected to vest	$104.20

Stock_Option_Plans_Stock_Optio1

Stock Option Plans - Stock Options Outstanding and Exercisable (Detail) (USD $)	9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	3 years 9 months 29 days
Option Outstanding, Weighted Average Exercise Price	$31.29	$28.80
Range One [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$10.58
Range of Exercise Prices, maximum	$27.25
Option Outstanding, Number Outstanding	2.9
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	2 years 9 months 11 days
Option Outstanding, Weighted Average Exercise Price	$25.87
Options Exercisable, Number Exercisable	2.1
Option Exercisable, Weighted Average Exercise Price	$25.88
Range Two [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$27.35
Range of Exercise Prices, maximum	$30.95
Option Outstanding, Number Outstanding	2.4
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	2 years 6 months 22 days
Option Outstanding, Weighted Average Exercise Price	$29.73
Options Exercisable, Number Exercisable	1.7
Option Exercisable, Weighted Average Exercise Price	$29.44
Range Three [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$31.24
Range of Exercise Prices, maximum	$35.71
Option Outstanding, Number Outstanding	1.5
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	4 years 11 months 1 day
Option Outstanding, Weighted Average Exercise Price	$35.40
Options Exercisable, Number Exercisable	0.1
Option Exercisable, Weighted Average Exercise Price	$32.95
Range Four [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$35.95
Range of Exercise Prices, maximum	$35.95
Option Outstanding, Number Outstanding
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	5 years 10 months 2 days
Option Outstanding, Weighted Average Exercise Price	$35.95
Options Exercisable, Number Exercisable
Option Exercisable, Weighted Average Exercise Price
Range Five [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$39.17
Range of Exercise Prices, maximum	$39.17
Option Outstanding, Number Outstanding	1.7
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	6 years 5 months 12 days
Option Outstanding, Weighted Average Exercise Price	$39.17
Options Exercisable, Number Exercisable
Option Exercisable, Weighted Average Exercise Price
Range Six [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$10.58
Range of Exercise Prices, maximum	$39.17
Option Outstanding, Number Outstanding	8.5
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	3 years 9 months 29 days
Option Outstanding, Weighted Average Exercise Price	$31.29
Options Exercisable, Number Exercisable	3.9
Option Exercisable, Weighted Average Exercise Price	$27.67

Deferred_Compensation_Addition

Deferred Compensation - Additional information (Detail) (USD $)	3 Months Ended					9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Mar. 31, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
						Y
Compensation And Retirement Disclosure [Abstract]
Deferred Equity Participation Plan, distributions to key executives, age						Age 62 (or the one-year anniversary of the date of the grant for participants over the age of 61 as of the grant date) or upon or after their actual retirement
Minimum age of employee on Grant Date for participation in plan						61
Compensation approved by committee, value			$8		$7.30
Fair value of the funded cash award assets								41.6
Charge to compensation expenses related to awards	2			1.5		5.3	4.1
Cash and equity awards with aggregate fair value vested and distributed to participants						0.7	0.7
Unearned deferred compensation, value						30		5.6
Unearned deferred compensation, shares						2		0.8
Total intrinsic value of unvested equity based awards						89.2		21.1
Common stock Purchased from open Market, Share		1.2
Common stock Purchased from open Market, Value		$52.40

Restricted_Stock_and_Cash_Awar1

Restricted Stock and Cash Awards - Additional Information (Detail) (USD $)

1 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

In Millions, except Share data, unless otherwise specified

Mar. 02, 2010

Sep. 30, 2013

Dec. 31, 2012

Mar. 13, 2013

Mar. 13, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

Jun. 30, 2013

Jun. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Mar. 31, 2013

Mar. 13, 2013

Mar. 31, 2012

Mar. 16, 2012

Mar. 08, 2011

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Employees

award

Minimum [Member]

Executive Officer [Member]

Restricted Stock Units (RSUs) [Member]

Restricted Stock Units (RSUs) [Member]

Restricted Stock Units (RSUs) [Member]

Restricted Stock Units (RSUs) [Member]

Restricted Stock Units (RSUs) [Member]

Restricted Stock Units (RSUs) [Member]

Restricted Stock Units (RSUs) [Member]

Restricted Stock Units (RSUs) [Member]

Restricted Stock Units (RSUs) [Member]

Restricted Stock Units (RSUs) [Member]

Cash Awards [Member]

Cash Awards [Member]

Cash Awards [Member]

Cash Awards [Member]

Cash Awards [Member]

Cash Awards [Member]

Cash Awards [Member]

Cash Awards [Member]

2009 Provisional Cash Awards [Member]

Unvested Restricted Stock [Member]

Unvested Restricted Stock [Member]

2012 Provisional Cash Awards [Member]

2012 Provisional Cash Awards [Member]

2011 Provisional Cash Awards [Member]

2011 Provisional Cash Awards [Member]

2011 Provisional Cash Awards [Member]

2011 Provisional Cash Awards [Member]

Y

Minimum [Member]

Executive Officer [Member]

Minimum [Member]

Executive Officer [Member]

Officer and Key Employees [Member]

Officer and Key Employees [Member]

Officer and Key Employees [Member]

Officer and Key Employees [Member]

Officer and Key Employees [Member]

Officer and Key Employees [Member]

Y

Y

Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]

Share-based compensation, shares outstanding, Value

$1.20

$1.20

Share-based compensation, shares outstanding

8,500,000

9,000,000

500,000

500,000

Shares granted in the period

17,500

345,000

20,000

332,000

Fair value of grants in period

0.8

13.5

0.7

11.9

Share based payment award vesting date

13-Mar-17

16-Mar-16

Minimum age of employee with not subject to award forfeiture on condition compliance

55

55

55

Period of Service from Grant Date Stock Options Awarded Not Subject to Forfeiture

2 years

2 years

2 years

Restricted stock or unit expense

2.3

1.7

7.4

5.5

Total intrinsic value

46.4

33.8

Equity awards with an aggregate fair value

8.4

7.2

Provisional compensation cash award approved for future grant by compensation committee, value

10.5

13.1

14.4

Provisional compensation cash award approved for future grant by compensation committee, units

365,000

269,000

432,000

368,000

464,000

1,100,000

Performance period, years

1

Vesting period, years

2 years

Ultimate award value, multiples of original value of the units, minimum

0.5

Ultimate award value, multiples of original value of the units, maximum

1.5

Cash-based compensation award, expenses

2

5.4

2.6

1.9

6.9

5.7

Future grant of provisional cash awards

17

Aggregate units

706,000

Grants vested in period fair value

$26.50

Retirement_Plans_Components_of

Retirement Plans - Components of Net Periodic Pension Benefit Cost (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Compensation And Retirement Disclosure [Abstract]
Service cost	$0.20	$0.10	$0.40	$0.30
Interest cost on benefit obligation	2.9	3	8.8	9
Expected return on plan assets	-4.2	-3.8	-12.8	-11.4
Amortization of net actuarial loss	2	1.8	5.9	5.4
Net periodic benefit cost	$0.90	$1.10	$2.30	$3.30

Retirement_Plans_Additional_In

Retirement Plans - Additional Information (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Compensation And Retirement Disclosure [Abstract]
Minimum contribution by employer	$0	$0
Discretionary contributions by employer	$6.30	$5.40

Investments_Investments_Report

Investments - Investments Reported in Other Current and Non-Current Assets (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Schedule of Equity Method Investments [Line Items]
Funding Commitments	$10.60
Assets	87.5	54.1
Chem-Mod LLC [Member]
Schedule of Equity Method Investments [Line Items]
Funding Commitments
Assets	4	4
Chem-Mod International LLC [Member]
Schedule of Equity Method Investments [Line Items]
Funding Commitments
Assets	2	2
C-Quest Technology LLC [Member]
Schedule of Equity Method Investments [Line Items]
Funding Commitments
Assets	2
Clean-Coal Investments [Member] | Nine 2009 Era Clean Coal Plants [Member]
Schedule of Equity Method Investments [Line Items]
Funding Commitments	1.8
Assets	8.2	2.8
Clean-Coal Investments [Member] | Five 2009 Era Clean Coal Plants [Member]
Schedule of Equity Method Investments [Line Items]
Funding Commitments	0.9
Assets	6.8	6.3
Clean-Coal Investments [Member] | Five 2011 Era Clean Coal Production Plants [Member]
Schedule of Equity Method Investments [Line Items]
Funding Commitments
Assets	12.1	13.2
Clean-Coal Investments [Member] | Nine 2011 Era Clean Coal Production Plants [Member]
Schedule of Equity Method Investments [Line Items]
Funding Commitments	2.2
Assets	41.4	9.2
Clean-Coal Investments [Member] | Six 2011 Era Clean Coal Production Plants [Member]
Schedule of Equity Method Investments [Line Items]
Funding Commitments	0.7
Assets	7.4	5.1
Clean-Coal Investments [Member] | Notes Receivable and Interest from Co-Investor [Member]
Schedule of Equity Method Investments [Line Items]
Funding Commitments
Assets		8.5
Other Investments [Member]
Schedule of Equity Method Investments [Line Items]
Funding Commitments	5
Assets	$3.60	$3

Investments_Investments_Report1

Investments - Investments Reported in Other Current and Non-Current Assets (Parenthetical) (Detail) (Clean-Coal Investments [Member])	9 Months Ended
	Sep. 30, 2013
	Plant
	Entity
Nine 2009 Era Clean Coal Plants [Member]
Schedule of Equity Method Investments [Line Items]
Number of coal plants	9
Number of variable interest entities	4
Five 2009 Era Clean Coal Plants [Member]
Schedule of Equity Method Investments [Line Items]
Number of coal plants	5
Number of variable interest entities	2
Five 2011 Era Clean Coal Production Plants [Member]
Schedule of Equity Method Investments [Line Items]
Number of coal plants	5
Number of variable interest entities	6
Nine 2011 Era Clean Coal Production Plants [Member]
Schedule of Equity Method Investments [Line Items]
Number of coal plants	9
Number of variable interest entities	5
Six 2011 Era Clean Coal Production Plants [Member]
Schedule of Equity Method Investments [Line Items]
Number of coal plants	6
Notes Receivable and Interest from Co-Investor [Member]
Schedule of Equity Method Investments [Line Items]
Number of plants sold	3

Investments_Additional_Informa

Investments - Additional Information (Detail) (USD $)

3 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

In Millions, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 01, 2013

Mar. 01, 2013

Dec. 31, 2012

Sep. 01, 2013

Sep. 30, 2013

Mar. 01, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2014

Sep. 30, 2013

Dec. 31, 2014

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Aug. 01, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 28, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Venture

Plant

Notes Payable, Other Payables [Member]

2009 Era Plants [Member]

2009 Era Plants [Member]

2011 Era Plants [Member]

Chem-Mod International LLC [Member]

Clean-Coal Investments [Member]

Clean-Coal Investments [Member]

Clean-Coal Investments [Member]

Clean-Coal Investments [Member]

Clean-Coal Investments [Member]

Clean-Coal Investments [Member]

Clean-Coal Investments [Member]

Clean-Coal Investments [Member]

Clean-Coal Investments [Member]

Clean-Coal Investments [Member]

Chem-Mod Clean-Coal Venture [Member]

C-Quest Technology LLC [Member]

C-Quest Technology LLC [Member]

C-Quest Technology LLC [Member]

C-Quest Technology LLC [Member]

Chem-Mod LLC [Member]

Chem-Mod LLC [Member]

Chem-Mod LLC [Member]

Chem-Mod LLC [Member]

Chem-Mod Clean-Coal Venture - U.S. And Canadian Operations [Member]

Long Term Production Contracts [Member]

Noncontrolling Interest [Member]

Long-Term Production Agreement [Member]

Other Investments [Member]

Other Investments [Member]

Other Investments [Member]

Other Investments [Member]

Other Investments [Member]

Investment Management Company [Member]

Investment

Venture

Plant

Notes Payable, Other Payables [Member]

Notes Receivable and Interest from Co-Investor [Member]

Notes Receivable and Interest from Co-Investor [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

VIE [Member]

2009 Era Plants [Member]

2011 Era Plants [Member]

Change In Option On Delivery Of Additional Interest [Member]

Plant

2009 Era Plants [Member]

2011 Era Plants [Member]

Plant

Plant

Plant

Four Venture Capital Funds [Member]

Variable Interest Entity, Not Primary Beneficiary [Member]

Variable Interest Entity, Not Primary Beneficiary [Member]

Investment

Plant

Scenario, Forecast [Member]

Scenario, Forecast [Member]

Plant

Plant

Plant

Plant

Twelve Certified Low-Income Housing Developments [Member]

Schedule of Equity Method Investments [Line Items]

Ownership interest acquired in a limited liability company

99.00%

31.52%

8.00%

46.54%

20.00%

Total assets of variable interest entities

$6.10

Total liabilities of variable interest entities

0.6

Total revenue of limited liability companies

255.7

27.1

Total expenses of limited liability companies

291.9

15.2

Non-controlling interest

13.7

Options to acquire additional interest, percent

19.00%

15.00%

Options to acquire additional interest, total price

9.5

7.5

End date for acquiring additional interest

15-Aug-16

Loans to majority owners

2

Interest rate of loan

2.00%

Maturity date of of loan

15-May-14

Loan description

On August 1, 2013, we loaned the majority owner $2.0 million at a 2% interest rate, which matures on May 15, 2014. The loan can be paid in cash or by delivery of an additional 4% ownership interest in C-Questbs global operations. If the loan is paid by delivery of the additional 4% ownership interest, our option would be reduced to 15% and the remaining purchase price would be reduced to $7.5 million.

Delivery of additional ownership interest

4.00%

Number of clean coal production plants owned

3

34

14

20

28

14

6

Number of additional plants acquired

12

Number of additional plants acquired with ownership interest range one

9

Number of additional plants acquired with ownership interest range two

3

Ownership interest before additional nine plants acquired

24.50%

Ownership interest after additional nine plants acquired

49.50%

Ownership interest before additional three plants acquired

25.00%

Ownership interest after additional three plants acquired

60.00%

Total revenues

835.8

650.4

2,289.40

1,847.10

68.4

6.3

Total expenses

750.3

574.1

2,064.20

1,647.20

72.3

6.9

Purchase of consideration received

8

8

Payment of cash and other consideration

5

5

Gain on purchase of additional interest

9.6

9.6

Prior percentage of equity interest in limited liability company

25.00%

25.00%

Additional percentage of equity interest in limited liability company upon acquisition

35.00%

35.00%

Fixed assets and other amortizable intangible assets acquired upon acquisition

26.3

26.3

Carrying value of prior non-controlling interest in limited liability company on acquisition date

4.8

4.8

Other assets acquired upon acquisition

5

5

Amount of promissory note

10

Purchase price paid in cash

4

Interest rate on promissory note

3.00%

Number of clean coal production plants seeking and negotiating for long term production contract

6

Number of variable interest entities

9

5

Total assets of limited liability companies

80.4

Total liability of limited liability companies

37.8

Additional investment per plant under new long-term production contract, net of co-investor funds

5

30

35

Tax effected average additional investment

2.5

Investment in engineering and construction contracts

5.6

5.6

Idle period during move and redeployment

12 months

18 months

Assets

87.5

87.5

54.1

8.5

2

4

4

3.6

3

3.2

60

Cost of acquiring equity interest

0.5

Carrying value of investments

0

Liabilities

20

Non controlling interest in venture capital funds number

5

5

Non controlling interest certified low-income housing developments

12

12

Non controlling interest in real estate entities

2

2

Carrying value of investments

$0

$0

Commitments_Contingencies_and_2

Commitments, Contingencies and Off-Balance Sheet Arrangements - Contractual Obligations (Detail) (USD $)	Sep. 30, 2013
In Millions, unless otherwise specified
Note Purchase Agreements [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2013
Contractual Obligations, Payments Due by Period, 2014	100
Contractual Obligations, Payments Due by Period, 2015
Contractual Obligations, Payments Due by Period, 2016	50
Contractual Obligations, Payments Due by Period, 2017	300
Contractual Obligations, Payments Due by Period, Thereafter	475
Total	925
Credit Agreement [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2013	135.5
Contractual Obligations, Payments Due by Period, 2014
Contractual Obligations, Payments Due by Period, 2015
Contractual Obligations, Payments Due by Period, 2016
Contractual Obligations, Payments Due by Period, 2017
Contractual Obligations, Payments Due by Period, Thereafter
Total	135.5
Interest on Debt [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2013	8.1
Contractual Obligations, Payments Due by Period, 2014	50.4
Contractual Obligations, Payments Due by Period, 2015	44.1
Contractual Obligations, Payments Due by Period, 2016	44.1
Contractual Obligations, Payments Due by Period, 2017	41.2
Contractual Obligations, Payments Due by Period, Thereafter	76.6
Total	264.5
Total Debt Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2013	143.6
Contractual Obligations, Payments Due by Period, 2014	150.4
Contractual Obligations, Payments Due by Period, 2015	44.1
Contractual Obligations, Payments Due by Period, 2016	94.1
Contractual Obligations, Payments Due by Period, 2017	341.2
Contractual Obligations, Payments Due by Period, Thereafter	551.6
Total	1,325
Operating Lease Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2013	18.8
Contractual Obligations, Payments Due by Period, 2014	69.4
Contractual Obligations, Payments Due by Period, 2015	61.8
Contractual Obligations, Payments Due by Period, 2016	50.6
Contractual Obligations, Payments Due by Period, 2017	40.2
Contractual Obligations, Payments Due by Period, Thereafter	109.3
Total	350.1
Less Sublease Arrangements [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2013	-2.1
Contractual Obligations, Payments Due by Period, 2014	-1.8
Contractual Obligations, Payments Due by Period, 2015	-0.8
Contractual Obligations, Payments Due by Period, 2016	-0.1
Contractual Obligations, Payments Due by Period, 2017
Contractual Obligations, Payments Due by Period, Thereafter
Total	-4.8
Outstanding Purchase Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2013	4.1
Contractual Obligations, Payments Due by Period, 2014	9.4
Contractual Obligations, Payments Due by Period, 2015	7
Contractual Obligations, Payments Due by Period, 2016	1.3
Contractual Obligations, Payments Due by Period, 2017	0.3
Contractual Obligations, Payments Due by Period, Thereafter
Total	22.1
Total Contractual Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2013	164.4
Contractual Obligations, Payments Due by Period, 2014	227.4
Contractual Obligations, Payments Due by Period, 2015	112.1
Contractual Obligations, Payments Due by Period, 2016	145.9
Contractual Obligations, Payments Due by Period, 2017	381.7
Contractual Obligations, Payments Due by Period, Thereafter	660.9
Total	$1,692.40

Commitments_Contingencies_and_3

Commitments, Contingencies and Off-Balance Sheet Arrangements - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		141 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
	Entity	Entity	LetterOfCredit	Entity	Entity
	sqft		Entity
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Acquired property through lease area, sqft.	306,000
Acquired property through lease percentage of building	60.00%
Operating lease commitment, expiration date	28-Feb-18
Number of companies acquired	20	12	53	31	265
Aggregate amount of maximum earnout obligations related to acquisitions			$400.40
Aggregate amount of maximum earnout obligations related to acquisitions, recorded in consolidated balance sheet			140.4
Liabilities recorded on self-insurance	8.7		8.7		8.7
Number of letters of credit issued			2
Income tax credits and adjustments			130
Errors and Omissions [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Insurance claims, amount retained			5
Amount of losses in excess of retained amounts	175		175		175
Minimum [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Ownership interest	1.00%		1.00%		1.00%
Minimum [Member] | Errors and Omissions [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Actuarial range value	1.7		1.7		1.7
Maximum [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Ownership interest	50.00%		50.00%		50.00%
Maximum [Member] | Errors and Omissions [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Actuarial range value	4.9		4.9		4.9
Tax-Advantaged Investments No Longer Held [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Total indemnifications	45		45		45
Letter of Credit [Member] | Self-Insurance Deductibles [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Debt	9.5		9.5		9.5
Letter of Credit [Member] | Rent-A-Captive Facility [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Debt	$5.70		$5.70		$5.70

Commitments_Contingencies_and_4

Commitments, Contingencies and Off-Balance Sheet Arrangements - Off-Balance Sheet Commitments (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
Letters of Credit [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Amount of Commitment Expiration by Period - 2013
Amount of Commitment Expiration by Period - 2014
Amount of Commitment Expiration by Period - 2015
Amount of Commitment Expiration by Period - 2016
Amount of Commitment Expiration by Period - 2017
Amount of Commitment Expiration by Period - Thereafter	15.2
Total Amounts Committed	15.2
Financial Guarantees [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Amount of Commitment Expiration by Period - 2013
Amount of Commitment Expiration by Period - 2014
Amount of Commitment Expiration by Period - 2015
Amount of Commitment Expiration by Period - 2016
Amount of Commitment Expiration by Period - 2017
Amount of Commitment Expiration by Period - Thereafter	9.3
Total Amounts Committed	9.3
Funding Commitments [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Amount of Commitment Expiration by Period - 2013	7
Amount of Commitment Expiration by Period - 2014	0.7
Amount of Commitment Expiration by Period - 2015
Amount of Commitment Expiration by Period - 2016
Amount of Commitment Expiration by Period - 2017
Amount of Commitment Expiration by Period - Thereafter	2.9
Total Amounts Committed	10.6
Total Commitments [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Amount of Commitment Expiration by Period - 2013	7
Amount of Commitment Expiration by Period - 2014	0.7
Amount of Commitment Expiration by Period - 2015
Amount of Commitment Expiration by Period - 2016
Amount of Commitment Expiration by Period - 2017
Amount of Commitment Expiration by Period - Thereafter	27.4
Total Amounts Committed	$35.10

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Earnings - Schedule of Accumulated Comprehensive Loss (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
In Millions, unless otherwise specified			Pension Liability [Member]	Foreign Currency Translation [Member]	Fair Value of Derivative Investments [Member]	Accumulated Other Comprehensive Loss [Member]
Comprehensive Earnings [Line Items]
Balance	$1,932.20	$1,658.60	($52.40)	$20.50	($0.90)	($32.80)
Net change in period			0.4	-9.9	0.5	-9
Balance	$1,932.20	$1,658.60	($52)	$10.60	($0.40)	($41.80)

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Earnings - Additional Information (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Expense related to pension liability reclassified from accumulated other comprehensive loss	$5.90	$5.40
Income (expense) related to fair value of derivative investments reclassified from accumulated other comprehensive loss	0.6	-0.1
Foreign currency translation reclassified from accumulated other comprehensive loss	$0	$0

Segment_Information_Additional

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
	Segment
Segment Reporting [Abstract]
Number of reportable operating segments	3

Segment_Information_Schedule_o

Segment Information - Schedule of Segment Reporting Information by Segment (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Total revenues	$835.80	$650.40	$2,289.40	$1,847.10
Identifiable assets at September 30, 2013 and 2012	5,970.20		5,970.20		5,352.30
Brokerage [Member]
Segment Reporting Information [Line Items]
Total revenues	546.3	479.7	1,551.60	1,338.50
Earnings before income taxes	97.3	82	250.5	203.8
Identifiable assets at September 30, 2013 and 2012	4,661.90	3,835	4,661.90	3,835
Risk Management [Member]
Segment Reporting Information [Line Items]
Total revenues	149.7	142.2	459.5	426.9
Earnings before income taxes	17.9	18.2	59.6	54.9
Identifiable assets at September 30, 2013 and 2012	546.2	547.9	546.2	547.9
Corporate [Member]
Segment Reporting Information [Line Items]
Total revenues	139.8	28.5	278.3	81.7
Earnings before income taxes	-29.7	-23.9	-84.9	-58.8
Identifiable assets at September 30, 2013 and 2012	$762.10	$626.40	$762.10	$626.40