CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings (Accumulated Deficit). Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings (Accumulated Deficit).	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Cumulative Effect, Period of Adoption, Adjustment	Total
Beginning balance at Dec. 31, 2018	$ 49	$ 1,080,084		$ (72,167)	$ (6,812)	$ (6,190)		$ 994,964
Beginning Balance (in shares) at Dec. 31, 2018	48,874,836
Increase (decrease) in shareholders' equity
Net income				74,382				74,382
Other comprehensive income (loss)					24,203			24,203
Repurchase of stock						(13,323)		(13,323)
Repurchase of stock (in shares)	(527,396)
Issuance of treasury stock for employee stock purchase plan		100				389		489
Issuance of treasury stock for employee stock purchase plan (in shares)	20,528
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax		(2,541)				345		(2,196)
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax (in shares)	91,032
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax		(97)				1,621		1,524
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax (in shares)	13,125
Cash dividends common stock				(33,579)				(33,579)
Stock dividend equivalents restricted stock units		504		(504)
Stock-based compensation		3,236						3,236
Stock issued in acquisition of Banc Ed, net of stock issuance costs	$ 7	166,274						166,281
Stock issued in acquisition of Banc Ed, net of stock issuance costs (in shares)	6,725,152
Ending balance at Sep. 30, 2019	$ 56	1,247,560		(31,868)	17,391	(17,158)		1,215,981
Ending Balance (in shares) at Sep. 30, 2019	55,197,277
Beginning balance at Jun. 30, 2019	$ 56	1,246,160		(44,878)	14,627	(12,357)		1,203,608
Beginning Balance (in shares) at Jun. 30, 2019	55,386,636
Increase (decrease) in shareholders' equity
Net income				24,828				24,828
Other comprehensive income (loss)					2,764			2,764
Repurchase of stock						(4,890)		(4,890)
Repurchase of stock (in shares)	(194,062)
Issuance of treasury stock for employee stock purchase plan		21				83		104
Issuance of treasury stock for employee stock purchase plan (in shares)	4,378
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax		(6)						(6)
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax		(6)				6
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax (in shares)	325
Cash dividends common stock				(11,632)				(11,632)
Stock dividend equivalents restricted stock units		186		(186)
Stock-based compensation		1,205						1,205
Ending balance at Sep. 30, 2019	$ 56	1,247,560		(31,868)	17,391	(17,158)		1,215,981
Ending Balance (in shares) at Sep. 30, 2019	55,197,277
Beginning balance at Dec. 31, 2019	$ 56	1,248,216		(14,813)	14,960	(27,985)		1,220,434
Beginning Balance (in shares) at Dec. 31, 2019	54,788,772
Increase (decrease) in shareholders' equity
Net income				71,999				71,999
Other comprehensive income (loss)					20,565			20,565
Repurchase of stock						(9,669)		(9,669)
Repurchase of stock (in shares)	(407,850)
Issuance of treasury stock for employee stock purchase plan		(68)				504		436
Issuance of treasury stock for employee stock purchase plan (in shares)	26,651
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax		(2,648)				2,013		(635)
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax (in shares)	106,589
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax		(51)				152		101
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax (in shares)	8,069
Cash dividends common stock				(36,017)				(36,017)
Stock dividend equivalents restricted stock units		529		(529)
Stock-based compensation		4,413						4,413
Ending balance at Sep. 30, 2020	$ 56	1,250,391	$ (15,922)	4,718	35,525	(34,985)	$ (15,922)	1,255,705
Ending Balance (in shares) at Sep. 30, 2020	54,522,231
Beginning balance at Jun. 30, 2020	$ 56	1,248,045		(13,951)	37,037	(35,103)		1,236,084
Beginning Balance (in shares) at Jun. 30, 2020	54,516,000
Increase (decrease) in shareholders' equity
Net income				30,829				30,829
Other comprehensive income (loss)					(1,512)			(1,512)
Issuance of treasury stock for employee stock purchase plan		(23)				116		93
Issuance of treasury stock for employee stock purchase plan (in shares)	6,119
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax		(2)				2
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax (in shares)	112
Cash dividends common stock				(11,994)				(11,994)
Stock dividend equivalents restricted stock units		166		(166)
Stock-based compensation		2,205						2,205
Ending balance at Sep. 30, 2020	$ 56	$ 1,250,391	$ (15,922)	$ 4,718	$ 35,525	$ (34,985)	$ (15,922)	$ 1,255,705
Ending Balance (in shares) at Sep. 30, 2020	54,522,231