Share-Based Compensation - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) shares	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) yr shares	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 12,209	$ 6,442	$ 26,148	$ 18,181
Share-based Compensation			20,433	15,426
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	2,381	2,065	$ 7,057	6,605
Look back period of stock price volatility			6 years
Cash received from stock option exercises			$ 3,600
Total unrecognized stock option expense	10,200		$ 10,200
Unrecognized compensation expense expected to be recognized period, years			1 year 3 months 15 days
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	3,648	3,736		8,821
Share-based Compensation			$ 9,601	8,800
Total unrecognized stock option expense	16,800		$ 16,800
Unrecognized compensation expense expected to be recognized period, years			1 year 5 months 1 day
Stock units vesting period			3 years
Phantom Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	376	253	$ 740	2,196
Stock units vesting period			3 years
Deferred Compensation Share-based Arrangements, Liability, Current and Noncurrent	1,500		$ 1,500		$ 800
Share based compensation, cash settlement			300
Phantom Shares [Member] | Parent Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense			400	300
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	4,196	388	$ 4,975	559
Stock units vesting period			3 years
Deferred Compensation Share-based Arrangements, Liability, Current and Noncurrent	6,100		$ 6,100		$ 1,100
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	1,608	$ 0	3,775	$ 0
Total unrecognized stock option expense	$ 2,500		$ 2,500
Unrecognized compensation expense expected to be recognized period, years	1 year 10 months 21 days
Allocated Share-based Compensation Expense, Expected Payout Percentage	180.00%		180.00%
2012 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award vesting on the first anniversary of the grant date			33.33%
Percentage of award vesting on the second anniversary of the grant date			33.33%
Percentage of award vesting on the third anniversary of the grant date			33.33%
Service period after reaching the age of 55			10 years
Age Requirement For Vesting Provision After Service Period | yr			55
2012 Stock Incentive Plan [Member] | Common Stock - Class A [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance | shares	26,850,000		26,850,000
Minimum [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Duration of U.S. Treasury Yields use to Calculate Average Implied Yield			5 years
Maximum [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Duration of U.S. Treasury Yields use to Calculate Average Implied Yield			7 years
Former Parent [Member] | Minimum [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payout Range Cash Performance Units			0.00%
Former Parent [Member] | Maximum [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payout Range Cash Performance Units			200.00%
Vesting Tranche 1 [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units vesting period			1 year
Allocated Share-based Compensation Expense, Percentage of Award Recognized			100.00%
Vesting Tranche 2 [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units vesting period			2 years
Allocated Share-based Compensation Expense, Percentage of Award Recognized			50.00%
Vesting Tranche 3 [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units vesting period			3 years
Allocated Share-based Compensation Expense, Percentage of Award Recognized			33.30%