CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated (Deficit)	Accumulated Other Comprehensive Income (loss)	Treasury Stock	Total
Beginning Balance at Dec. 31, 2017	$ 49	$ 1,084,889	$ (132,122)	$ (2,810)	$ (15,003)	$ 935,003
Beginning Balance (in shares) at Dec. 31, 2017						48,684,943
Increase (decrease) in shareholders' equity
Net income			21,917			$ 21,917
Other comprehensive loss				(6,259)		(6,259)
Tax Cuts and Jobs Act of 2017 reclassification			605	(605)
Issuance of treasury stock for employee stock purchase plan		(248)			494	$ 246
Issuance of treasury stock for employee stock purchase plan (in shares)						8,718
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax		(1,206)			1,336	$ 130
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax (in shares)						23,578
Cash dividends common stock at $0.20 and $0.21 per share for the three months ended March 31, 2018 and 2019, respectively			(9,739)			$ (9,739)
Stock dividend equivalents restricted stock units at $0.20 and $0.21 per share for the three months ended March 31, 2018 and 2019, respectively		128	(128)
Stock-based compensation		848				848
Ending Balance at Mar. 31, 2018	49	1,084,411	(119,467)	(9,674)	(13,173)	$ 942,146
Ending Balance (in shares) at Mar. 31, 2018						48,717,239
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			25,469			$ 25,469
Other comprehensive loss				8,407		8,407
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
Issuance of treasury stock for employee stock purchase plan		50			222	$ 272
Issuance of treasury stock for employee stock purchase plan (in shares)						11,731
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax		(171)			171
Net issuance of treasury stock for restricted/deferred stock unit vesting and related tax (in shares)						9,070
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax		(72)			72
Net issuance of treasury stock for stock options exercised, net of shares redeemed and related tax (in shares)						3,838
Cash dividends common stock at $0.20 and $0.21 per share for the three months ended March 31, 2018 and 2019, respectively			(10,266)			$ (10,266)
Stock dividend equivalents restricted stock units at $0.20 and $0.21 per share for the three months ended March 31, 2018 and 2019, respectively		161	(161)
Stock-based compensation		1,014				1,014
Ending Balance at Mar. 31, 2019	$ 56	$ 1,247,340	$ (57,125)	$ 1,595	$ (5,725)	$ 1,186,141
Ending Balance (in shares) at Mar. 31, 2019						55,624,627