CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated (Deficit)	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	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			49,554			49,554
Other comprehensive income (loss)				21,439		21,439
Repurchase of stock					(8,433)	(8,433)
Repurchase of stock (in shares)	(333,334)
Issuance of treasury stock for employee stock purchase plan		79			306	385
Issuance of treasury stock for employee stock purchase plan (in shares)	16,150
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax		(2,535)			345	(2,190)
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		(91)			1,615	1,524
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax (in shares)	12,800
Cash dividends common stock			(21,947)			(21,947)
Stock dividend equivalents restricted stock units		318	(318)
Stock-based compensation		2,031				2,031
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 Jun. 30, 2019	$ 56	1,246,160	(44,878)	14,627	(12,357)	1,203,608
Ending Balance (in shares) at Jun. 30, 2019	55,386,636
Beginning balance at Mar. 31, 2019	$ 56	1,247,340	(57,125)	1,595	(5,725)	1,186,141
Beginning Balance (in shares) at Mar. 31, 2019	55,624,627
Increase (decrease) in shareholders' equity
Net income			24,085			24,085
Other comprehensive income (loss)				13,032		13,032
Repurchase of stock					(8,433)	(8,433)
Repurchase of stock (in shares)	(333,334)
Issuance of treasury stock for employee stock purchase plan		29			84	113
Issuance of treasury stock for employee stock purchase plan (in shares)	4,419
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax		(2,364)			174	(2,190)
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax (in shares)	81,962
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax		(19)			1,543	1,524
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax (in shares)	8,962
Cash dividends common stock			(11,681)			(11,681)
Stock dividend equivalents restricted stock units		157	(157)
Stock-based compensation		1,017				1,017
Ending balance at Jun. 30, 2019	$ 56	1,246,160	(44,878)	14,627	(12,357)	1,203,608
Ending Balance (in shares) at Jun. 30, 2019	55,386,636
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			41,170			41,170
Other comprehensive income (loss)				22,077		22,077
Repurchase of stock					(9,669)	(9,669)
Repurchase of stock (in shares)	(407,850)
Issuance of treasury stock for employee stock purchase plan		(45)			388	343
Issuance of treasury stock for employee stock purchase plan (in shares)	20,532
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax		(2,646)			2,011	(635)
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax (in shares)	106,477
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			(24,023)			(24,023)
Stock dividend equivalents restricted stock units		363	(363)
Stock-based compensation		2,208				2,208
Ending balance at Jun. 30, 2020	$ 56	1,248,045	(13,951)	37,037	(35,103)	1,236,084
Ending Balance (in shares) at Jun. 30, 2020	54,516,000
Beginning balance at Mar. 31, 2020	$ 56	1,249,301	(27,599)	33,101	(37,274)	1,217,585
Beginning Balance (in shares) at Mar. 31, 2020	54,401,208
Increase (decrease) in shareholders' equity
Net income			25,806			25,806
Other comprehensive income (loss)				3,936		3,936
Repurchase of stock, balance					3	3
Issuance of treasury stock for employee stock purchase plan		(7)			119	112
Issuance of treasury stock for employee stock purchase plan (in shares)	6,296
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax		(2,467)			1,907	(560)
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax (in shares)	100,968
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax		(41)			142	101
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax (in shares)	7,528
Cash dividends common stock			(11,968)			(11,968)
Stock dividend equivalents restricted stock units		190	(190)
Stock-based compensation		1,069				1,069
Ending balance at Jun. 30, 2020	$ 56	$ 1,248,045	(13,951)	$ 37,037	$ (35,103)	1,236,084
Ending Balance (in shares) at Jun. 30, 2020	54,516,000
Increase (decrease) in shareholders' equity
Cumulative change in accounting principal			$ (15,922)			$ (15,922)