Equity-Based Compensation - Restricted Stock (Details) - USD ($)	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Nonvested awards
Equity interests purchased	$ 787,000	$ 731,000
2015 Plan
Equity-based compensation
Shares authorized for issuance	7,120,000
Restricted stock
Nonvested awards
Equity interests purchased	$ 787,000
Unrecognized compensation
Unrecognized compensation costs	$ 48,500,000
Unrecognized compensation costs, weighted average period for recognition	2 years 7 months 6 days
Excess tax benefit related to equity awards recorded as increase to additional paid-in capital	$ 703,000
Restricted stock | 4-year service vesting
Nonvested awards
Granted (in shares)	340,291
Restricted stock | Service vesting, year 1
Vesting terms
Vesting percentage	20.00%
Restricted stock | Service vesting, year 2
Vesting terms
Vesting percentage	20.00%
Restricted stock | Service vesting, year 3
Vesting terms
Vesting percentage	30.00%
Restricted stock | Service vesting, year 4
Vesting terms
Vesting percentage	30.00%
Restricted stock | 3-year performance vesting (cliff)
Nonvested awards
Granted (in shares)	267,530
Restricted stock | 2015 Plan
Nonvested awards
Nonvested at beginning of period (in shares)	2,255,681
Granted (in shares)	607,821
Vested (in shares)	(335,395)
Forfeited (in shares)	(22,119)
Nonvested at end of period (in shares)	2,505,988
Weighted Average Fair Value at Grant Date
Nonvested at beginning of period (in dollars per share)	$ 25.15
Granted (in dollars per share)	26.38
Vested (in dollars per share)	25.00
Forfeited (in dollars per share)	25.48
Nonvested at end of period (in dollars per share)	$ 25.47