Earnings Per Common Share - Computation of basic and diluted EPS - (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net income available to common shareholders	$ 99,473	$ 74,364	$ 47,865
Weighted Average Number of Shares Outstanding, Basic	23,966,000	23,897,000	19,866,000
Basic earnings per common share (in dollars per share)	$ 4.15	$ 3.11	$ 2.41
Diluted earnings per share:
Net income available to common shareholders	$ 99,473	$ 74,364	$ 47,865
Weighted Average Number of Shares Outstanding, Basic	23,966,000	23,897,000	19,866,000
Effect of dilutive securities (in shares)	258	257	211
Weighted-average dilutive shares	24,224,000	24,154,000	20,077,000
Diluted earnings per common share (in dollars per share)	$ 4.11	$ 3.08	$ 2.38