Net Income Per Common Share - (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Basic
Net income applicable to common stock	$ 23,179	$ 16,220	$ 67,295	$ 46,854
Average common shares outstanding (shares)	42,091,164	40,265,941	41,500,407	34,521,255
Net income per common share - basic (usd per share)	$ 0.55	$ 0.40	$ 1.62	$ 1.36
Diluted
Net income applicable to common stock	$ 23,179	$ 16,220	$ 67,295	$ 46,854
Average common shares outstanding (shares)	42,091,164	40,265,941	41,500,407	34,521,255
Effect of dilutive stock-based compensation (shares)	219,194	252,472	229,501	277,863
Average common shares outstanding - diluted (shares)	42,310,358	40,518,413	41,729,908	34,799,118
Net income per common share - diluted (usd per share)	$ 0.55	$ 0.40	$ 1.61	$ 1.35