Stock-Based Compensation Plans - Summary of Stock Option Activity (Details)	6 Months Ended
	Jun. 30, 2019 USD ($) $ / shares shares
Number of Shares
Outstanding, beginning balance (in shares) | shares	4,864,836
Exercised (in shares) | shares	(365,808)
Forfeited (in shares) | shares	(3,496)
Outstanding, ending balance (in shares) | shares	4,495,532
Exercisable, ending balance (in shares) | shares	3,951,380
Weighted Average Exercise Price
Beginning balance (in dollars per share) | $ / shares	$ 17.76
Exercised (in dollars per share) | $ / shares	15.90
Forfeited (in dollars per share) | $ / shares	17.89
Ending balance (in dollars per share) | $ / shares	17.91
Weighted average exercise price, exercisable, ending balance (in dollars per share) | $ / shares	$ 17.59
Weighted Average Remaining Contractual Term (Years)
Weighted average remaining contractual term, outstanding, end of period (in years)	5 years 9 months 7 days
Weighted average remaining contractual term, exercisable, end of period (in years)	5 years 6 months 14 days
Aggregate Intrinsic Value of In-the-Money Options
Aggregate intrinsic value of in-the-money options, outstanding, end of period | $	$ 73,859,896
Aggregate intrinsic value of in-the-money options, exercisable, end of period | $	$ 66,188,229