Share-Based Compensation - Stock Option Activity under Stock Option Plans (Details)	3 Months Ended	27 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares	Mar. 31, 2017 USD ($) $ / shares shares
Number of Shares
Beginning balance (in shares) | shares	260,211
Granted (in shares) | shares		0
Exercised (in shares) | shares	(80,835)
Cancelled (in shares) | shares
Ending balance (in shares) | shares	179,376	179,376
Vested and Expected to Vest (in shares) | shares	179,376	179,376
Exercisable (in shares) | shares	179,376	179,376
Weighted-Average Exercise Price
Beginning balance (in dollars per share) | $ / shares	$ 19.26
Granted (in dollars per share) | $ / shares
Exercised (in dollars per share) | $ / shares	22.76
Cancelled (in dollars per share) | $ / shares
Ending balance (in dollars per share) | $ / shares	17.68	$ 17.68
Vested and Expected to Vest (in dollars per share) | $ / shares	17.68	17.68
Exercisable (in dollars per share) | $ / shares	$ 17.68	$ 17.68
Weighted Average Remaining Contractual Term (in Years)
Outstanding (term)	2 years 10 months 10 days
Vested and Expected to Vest (term)	2 years 10 months 10 days
Exercisable (term)	2 years 10 months 10 days
Aggregate Intrinsic Value
Outstanding | $	$ 3,882,228	$ 3,882,228
Vested and Expected to Vest | $	3,882,228	3,882,228
Exercisable | $	$ 3,882,228	$ 3,882,228