Segment Revenues and Segment Income (Parenthetical) (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Segment Reporting Information [Line Items]
Share-based compensation expense	$ 13,719,000	$ 13,340,000	$ 27,581,000	$ 25,193,000
Corporate and Other
Segment Reporting Information [Line Items]
Share-based compensation expense	13,700,000	13,300,000	27,600,000	25,200,000
Severance expense	$ 8,000,000	$ 3,000,000	$ 13,500,000	$ 8,100,000