Condensed Consolidated Statements of Changes In Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance, shares at Dec. 31, 2015		220,171,091
Balance, value at Dec. 31, 2015	$ 3,849,334	$ 3,520,591	$ 331,301	$ (2,558)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	232,940		232,940
Other comprehensive loss, net of tax	(18,785)			(18,785)
Stock-based compensation	9,790	$ 9,790
Stock repurchased and retired, shares		(1,117,061)
Stock repurchased and retired, value	(17,708)	$ (17,708)
Issuances of common stock under stock plans and related net tax benefit, shares		1,123,000
Issuances of common stock under stock plans and related net tax benefit, value	2,626	$ 2,626
Cash dividends on common stock	$ (141,402)		(141,402)
Balance, shares at Dec. 31, 2016	220,177,030	220,177,030
Balance, value at Dec. 31, 2016	$ 3,916,795	$ 3,515,299	422,839	(21,343)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	102,815		102,815
Other comprehensive loss, net of tax	11,292			11,292
Stock-based compensation	4,275	$ 4,275
Stock repurchased and retired, shares		(339,012)
Stock repurchased and retired, value	(5,943)	$ (5,943)
Issuances of common stock under stock plans and related net tax benefit, shares		366,497
Issuances of common stock under stock plans and related net tax benefit, value	463	$ 463
Cash dividends on common stock	$ (70,852)		(70,852)
Balance, shares at Jun. 30, 2017	220,204,515	220,204,515
Balance, value at Jun. 30, 2017	$ 3,958,845	$ 3,514,094	$ 454,802	$ (10,051)