Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic and Diluted Earnings Per Share
Net Income		$ 57,410	$ 51,610	$ 52,392	$ 49,132	$ 49,599	$ 49,336	$ 44,384	$ 38,559	$ 210,544	$ 181,878	$ 116,377
Average outstanding shares - basic										88,255,290	83,603,515	77,537,664
Add: dilutive restricted stock units and stock options										130,485	73,670	69,941
Average outstanding shares - diluted										88,385,775	83,677,185	77,607,605
Basic earnings per share		$ 0.62	$ 0.57	$ 0.61	$ 0.58	$ 0.59	$ 0.58	$ 0.53	$ 0.48	$ 2.39	$ 2.18	$ 1.50
Diluted earnings per share		$ 0.62	$ 0.57	$ 0.61	$ 0.58	$ 0.59	$ 0.58	$ 0.52	$ 0.48	$ 2.38	$ 2.17	$ 1.50
Restricted stock units and stock options excluded from the diluted average outstanding share calculation	[1]									0	1,357	0

[1] Anti-dilution occurs when the unrecognized compensation cost per share of a restricted stock units or the exercise price of a stock option exceeds the market price of the Company’s stock.