Share-Based Compensation - Stock Option Activity (Details) - Stock options - 2012 Equity Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares
Options outstanding, beginning of period (in shares)	2,252,275	3,052,450	2,826,500
Granted (in shares)	20,000	140,000	385,200
Exercised (in shares)	(730,125)	(769,875)	(74,000)
Forfeited (in shares)	(12,350)	(170,300)	(85,250)
Options outstanding, end of period (in shares)	1,529,800	2,252,275	3,052,450	2,826,500
Options exercisable at period end (in shares)	1,163,150
Weighted- Average Exercise Price
Options outstanding, beginning balance (in dollars per share)	$ 16.92	$ 16.65	$ 15.69
Granted (in dollars per share)	20.48	19.40	23.38
Exercised (in dollars per share)	15.94	16.07	15.65
Forfeited (in dollars per share)	20.80	17.93	16.24
Options outstanding, ending balance (in dollars per share)	17.40	$ 16.92	$ 16.65	$ 15.69
Options exercisable at period end (in dollars per share)	$ 16.76
Options outstanding, weighted average contractual life	5 years 3 months 18 days	6 years 1 month 6 days	6 years 10 months 24 days	7 years 7 months 6 days
Options exercisable at period end, weighted average contractual life	4 years 9 months 18 days
Share-based Compensation Arrangement by Share-based Payment Award, Intrinsic Value [Roll Forward]
Options outstanding, intrinsic value	$ 13,479	$ 7,713	$ 16,421	$ 14,956
Exercised, intrinsic value	6,088	$ 4,754	$ 520
Options exercisable at period end, intrinsic value	$ 10,993