CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common stock	Paid-in capital	Treasury stock	Accumulated other comprehensive (loss) income	Retained earnings
Balance, beginning of period at Dec. 31, 2017		$ 370,567	$ 1,850,582	$ 0	$ (43,801)	$ 977,178
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net common stock issued under share-based compensation plans		781	(8,854)
Reissuance of treasury stock, net under share-based compensation plans			0	0
Equity compensation			5,272
Other comprehensive income (loss), net of tax	$ (63,959)				(63,959)
Net income	143,637					143,637
Balance, end of period at Mar. 31, 2018	3,231,403	371,348	1,847,000	0	(107,760)	1,120,815
Balance, beginning of period at Dec. 31, 2018	3,581,891	371,353	1,862,536	(175,059)	(124,214)	1,647,275
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net common stock issued under share-based compensation plans		0	0
Reissuance of treasury stock, net under share-based compensation plans			(11,582)	5,930
Equity compensation			5,282
Other comprehensive income (loss), net of tax	82,721				82,721
Net income	151,941					151,941
Balance, end of period at Mar. 31, 2019	$ 3,816,183	$ 371,353	$ 1,856,236	$ (169,129)	$ (41,493)	$ 1,799,216