Fair Value Measurements - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	$ 30,000,000	$ 0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	64,000,000
Business Combination, Contingent Consideration, Liability	3,000,000
Interest Rate Swap [Member]
Derivative, Number of Instruments Held	8
Derivative, Notional Amount			5,800,000,000
Derivative Liability	$ 17,000,000		$ 6,000,000