CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2017	$ 1,241,996	$ 458	$ 1,063,974	$ 177,149	$ 415
Balance (in shares) at Dec. 31, 2017		46,245,050
Increase (Decrease) in Stockholders' Equity
Net income	83,697			83,697
Other comprehensive income	(17,174)				(17,174)
Share-based compensation expense	6,362		6,362
Issuance of restricted stock, net	0
Issuance of restricted stock, net (in shares)		264,420
Common stock issued	601,171	$ 158	601,013
Common stock issued (in shares)		15,758,039
Restricted stock surrendered and canceled	(1,586)		(1,586)
Restricted stock surrendered and canceled (in shares)		(28,849)
Exercise of stock options	1,911	$ 1	1,910
Exercise of stock options (in shares)		234,061
Reclassification of certain tax effects of the Tax Cuts and Jobs Act	0			(82)	82
Balance at Sep. 30, 2018	1,916,377	$ 617	1,671,673	260,764	(16,677)
Balance (in shares) at Sep. 30, 2018		62,472,721
Balance at Jun. 30, 2018	1,288,525	$ 459	1,067,907	232,372	(12,213)
Balance (in shares) at Jun. 30, 2018		46,629,118
Increase (Decrease) in Stockholders' Equity
Net income	28,392			28,392
Other comprehensive income	(4,464)				(4,464)
Share-based compensation expense	2,445		2,445
Issuance of restricted stock, net	0
Issuance of restricted stock, net (in shares)		68,884
Common stock issued	601,171	$ 158	601,013
Common stock issued (in shares)		15,758,039
Restricted stock surrendered and canceled	(7)		(7)
Restricted stock surrendered and canceled (in shares)		(3,091)
Exercise of stock options	315	$ 0	315
Exercise of stock options (in shares)		19,771
Balance at Sep. 30, 2018	1,916,377	$ 617	1,671,673	260,764	(16,677)
Balance (in shares) at Sep. 30, 2018		62,472,721
Balance at Dec. 31, 2018	$ 1,969,697	$ 617	1,674,274	300,407	(5,601)
Balance (in shares) at Dec. 31, 2018	62,480,755	62,480,755
Increase (Decrease) in Stockholders' Equity
Net income	$ 118,620			118,620
Other comprehensive income	35,796				35,796
Repurchase and retirement of common stock	(100,000)	$ (33)	(89,887)	(10,080)
Repurchase and retirement of common stock (in shares)		(3,364,761)
Cash dividends declared	(40,807)			(40,807)
Dividend equivalents declared	0		89	(89)
Share-based compensation expense	7,927		7,927
Issuance of restricted stock, net	0
Issuance of restricted stock, net (in shares)		316,254
Restricted stock surrendered and canceled	(2,629)		(2,629)
Restricted stock surrendered and canceled (in shares)		(111,456)
Exercise of stock options	394		394
Exercise of stock options (in shares)		43,548
Balance at Sep. 30, 2019	$ 1,988,998	$ 584	1,590,168	368,051	30,195
Balance (in shares) at Sep. 30, 2019	59,364,340	59,364,340
Balance at Jun. 30, 2019	$ 1,984,456	$ 595	1,618,137	343,366	22,358
Balance (in shares) at Jun. 30, 2019		60,509,994
Increase (Decrease) in Stockholders' Equity
Net income	41,375			41,375
Other comprehensive income	7,837				7,837
Repurchase and retirement of common stock	(34,031)	$ (11)	(30,634)	(3,386)
Repurchase and retirement of common stock (in shares)		(1,145,515)
Cash dividends declared	(13,266)			(13,266)
Dividend equivalents declared	0		38	(38)
Share-based compensation expense	2,614		2,614
Issuance of restricted stock, net	0
Issuance of restricted stock, net (in shares)		11,500
Restricted stock surrendered and canceled	0		0
Restricted stock surrendered and canceled (in shares)		(12,250)
Exercise of stock options	13		13
Exercise of stock options (in shares)		611
Balance at Sep. 30, 2019	$ 1,988,998	$ 584	$ 1,590,168	$ 368,051	$ 30,195
Balance (in shares) at Sep. 30, 2019	59,364,340	59,364,340