Acquisition of Global Workplace Solutions (GWS) - Additional Information (Detail) - USD ($) $ in Thousands				3 Months Ended								12 Months Ended
	Sep. 04, 2015	Sep. 03, 2015	Aug. 13, 2015	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Aggregate principal amount issued												$ 595,440	$ 426,875	$ 800,000
Goodwill				$ 3,085,997				$ 2,333,821				3,085,997	2,333,821	2,290,474
Revenue				3,700,242	$ 2,712,559	$ 2,390,506	$ 2,052,503	2,787,194	$ 2,275,076	$ 2,126,806	$ 1,860,842	10,855,810	9,049,918	7,184,794
Operating income				206,983	240,101	228,755	160,105	288,627	185,140	206,006	112,481	835,944	792,254	616,128
Net income				$ 180,043	$ 149,123	$ 125,029	$ 92,937	$ 204,277	$ 107,099	$ 105,464	$ 67,663	547,132	484,503	316,538
Amortization expense												$ 175,300	138,100	$ 85,400
4.875% Senior Notes [Member]
Business Acquisition [Line Items]
Aggregate principal amount issued			$ 600,000
Interest rate of long-term debt			4.875%	4.875%								4.875%
Senior Notes due date												Mar. 01, 2026
2015 Credit Agreement [Member] | New Tranche B-1 and Tranche B-2 Term Loan Facilities [Member]
Business Acquisition [Line Items]
Aggregate principal amount issued	$ 400,000	$ 400,000										$ 400,000
Global Workplace Solutions (GWS) [Member]
Business Acquisition [Line Items]
Date of business purchase agreement												Sep. 01, 2015
Purchase price payable in cash				$ 1,475,000								$ 1,475,000
Business acquisition, acquisition date												Sep. 01, 2015
Goodwill				786,000								$ 786,000
Goodwill recorded in connection with acquisition deductible for tax purpose				$ 396,000								396,000
Revenue												982,000
Operating income												27,700
Net income												18,800
Direct transaction and integration cost												48,900
Amortization expense												24,200
Amortization expense of acquired intangible assets												48,300	72,500
Additional interest expense for debt incurred to finance acquisitions												22,400	$ 38,100
Removal of direct costs												48,900
Removal of tax impact												$ 48,900