Earnings Per Share - Reconciliation of Numerators and Denominators of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator for Earnings per Common Share-Basic:
Net Income									$ 71,392	$ 67,081	$ 57,910
Less: Income allocated to participating shares									225	280	165
Net Income Available to Common Shareholders	$ 17,659	$ 20,581	$ 17,059	$ 16,093	$ 17,423	$ 18,635	$ 18,188	$ 12,835	71,167	66,801	57,745
Numerator for Earnings per Common Share-Diluted:
Net Income									$ 71,392	$ 67,081	$ 57,910
Denominators:
Weighted Average Common Shares Outstanding-Basic (in shares)									34,677,738	33,812,990	29,683,103
Add: Dilutive potential common shares (in shares)									95,432	35,092	25,621
Denominator for Treasury Stock Method-Diluted (in shares)									34,773,170	33,848,082	29,708,724
Weighted Average Common Shares Outstanding-Basic (in shares)									34,677,738	33,812,990	29,683,103
Add: Average participating shares outstanding (in shares)									109,755	141,558	84,918
Denominator for Two-Class Method-Diluted (in shares)									34,787,493	33,954,548	29,768,021
Earnings per common share—basic (in USD per share)									$ 2.06	$ 1.98	$ 1.95
Earnings per common share—diluted (in USD per share)	$ 0.51	$ 0.59	$ 0.49	$ 0.46	$ 0.50	$ 0.54	$ 0.52	$ 0.41	2.05	1.98	1.95
Exercise price of warrants (in USD per share)	$ 31.53				$ 31,530.00				$ 31.53	$ 31,530.00	$ 31,530.00
Warrants
Denominators:
Anti-dilutive excluded from dilutive potential common shares (in shares)									517,012	517,012	517,012
Stock Options
Denominators:
Anti-dilutive excluded from dilutive potential common shares (in shares)									0	0	419,538
Restricted Stock
Denominators:
Anti-dilutive excluded from dilutive potential common shares (in shares)									116,749	106,466	59,297