Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands		Total	Common Stock	Capital Surplus	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Treasury Stock
Beginning Balance at Dec. 31, 2018		$ 2,228,470	$ 55,057	$ 1,054,601	$ 1,488,421	$ (95,782)	$ (273,827)
Total comprehensive (loss) income		135,887			57,744	78,143
Dividends		(14,769)			(14,769)
Purchase of treasury stock		(4,086)					(4,086)
Issuances of equity awards, net of forfeitures		604		2,383			(1,779)
Recognition of equity-based compensation		3,289		3,289
Sale of treasury stock		261		100			161
Exercise of stock options		1,187		257			930
Ending Balance at Mar. 31, 2019		2,350,843	55,057	1,060,630	1,531,396	(17,639)	(278,601)
Beginning Balance at Dec. 31, 2019		2,606,440	55,057	1,073,764	1,672,438	83,180	(277,999)
Total comprehensive (loss) income		132,771			(3,439)	136,210
Dividends		(15,209)			(15,209)
Purchase of treasury stock		(59,386)		(4,500)			(54,886)
Issuances of equity awards, net of forfeitures		593		521			72
Recognition of equity-based compensation		2,817		2,817
Sale of treasury stock		184		95			89
Exercise of stock options		2,270		392			1,878
Cumulative effect adjustments | ASU No. 2016-13 [Member]	[1]	(7,039)			(7,039)
Ending Balance at Mar. 31, 2020		$ 2,663,441	$ 55,057	$ 1,073,089	$ 1,646,751	$ 219,390	$ (330,846)

[1] Related to the adoption of ASU No. 2016-13. See Note 3, “New Accounting Pronouncements,” for further detail.