Stock-Based Compensation - Stock-Based Compensation Expense Recognized (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 33.3	$ 8.5	$ 83.2	$ 18.2
Corporate expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	9.6	5.2	28.1	8.5
Property, general, administrative, and other [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 23.7	$ 3.3	$ 55.1	$ 9.7