Shareholders' Equity - Stock Option Activity (Details) - Stock options - 2012 Equity Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, beginning of period (in shares)	2,484,400	2,165,000	1,190,000
Granted (in shares)	708,000	588,500	1,270,000
Exercised (in shares)	(196,000)	(16,600)	(28,750)
Forfeited (in shares)	(169,900)	(252,500)	(266,250)
Options outstanding, end of period (in shares)	2,826,500	2,484,400	2,165,000	1,190,000
Share-based Compensation Arrangement by Share-based Payment Award, Weighted Average Exercise Price [Roll Forward]
Options outstanding, weighted average exercise price, beginning balance (in dollars per share)	$ 16.22	$ 16.17	$ 15.48
Granted, weighted average exercise price (in dollars per share)	14.15	16.49	16.74
Exercised, weighted average exercise price (in dollars per share)	16.18	15.16	15.00
Forfeited, weighted average exercise price (in dollars per share)	16.38	16.57	15.88
Options outstanding, weighted average exercise price, ending balance (in dollars per share)	$ 15.69	$ 16.22	$ 16.17	$ 15.48
Share-based Compensation Arrangement by Share-based Payment Award, Intrinsic Value [Roll Forward]
Options outstanding, intrinsic value, beginning of period	$ 1,225	$ 1,890	$ 862
Exercised, intrinsic value	790	19	74
Options outstanding, intrinsic value, end of period	$ 14,956	$ 1,225	$ 1,890	$ 862
Options outstanding, weighted average contractual life	7 years 7 months 6 days	8 years 7 days	8 years 9 months 18 days	9 years 3 months 18 days
Options exercisable at period end (in shares)	1,245,375
Options exercisable at period end, weighted average exercise price (in dollars per share)	$ 15.94
Options exercisable at period end, weighted average contractual life	6 years 8 months 12 days
Options exercisable at period end, intrinsic value	$ 6,276