CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY Statement - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption					$ 67,642
Balance, beginning of period (value) at Jun. 30, 2017			$ 1,031	$ 452,016	1,585,278	$ (1,006,274)
Shares, beginning of period at Jun. 30, 2017			103,083,299
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for equity-based payment arrangements (value)			$ 1	174
Shares issued for equity-based payment arrangements (shares)			110,162
Tax withholding related to share-based compensation				(7,278)
Shares issued for Employee Stock Purchase Plan (value)			$ 0	5,370
Shares issued for Employee Stock Purchase Plan (shares)			55,948
Stock-based compensation expense				7,834
Net Income	$ 297,199				297,199
Dividends (value)					(76,429)
Purchase of treasury shares						(30,018)
Balance, end of period (value) at Mar. 31, 2018	$ 1,296,546		$ 1,032	458,116	1,873,690	(1,036,292)
Shares, end of period at Mar. 31, 2018			103,249,409
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share	$ 0.99
Cumulative Effect of New Accounting Principle in Period of Adoption					76,769
Balance, beginning of period (value) at Dec. 31, 2017			$ 1,032	452,841	1,756,419	(1,036,292)
Shares, beginning of period at Dec. 31, 2017			103,218,206
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for equity-based payment arrangements (value)			$ 0	175
Shares issued for equity-based payment arrangements (shares)			11,970
Tax withholding related to share-based compensation				(135)
Shares issued for Employee Stock Purchase Plan (value)			$ 0	2,010
Shares issued for Employee Stock Purchase Plan (shares)			19,233
Stock-based compensation expense				3,225
Net Income	$ 69,086				69,086
Dividends (value)					(28,584)
Purchase of treasury shares						0
Balance, end of period (value) at Mar. 31, 2018	$ 1,296,546		$ 1,032	458,116	1,873,690	(1,036,292)
Shares, end of period at Mar. 31, 2018			103,249,409
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share	$ 0.37
Preferred Shares		0
Cumulative Effect of New Accounting Principle in Period of Adoption					56,016
Balance, beginning of period (value) at Jun. 30, 2018	$ 1,322,844		$ 1,033	464,138	1,856,917	(1,055,260)
Shares, beginning of period at Jun. 30, 2018			103,278,562
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for equity-based payment arrangements (value)			$ 1	(1)
Shares issued for equity-based payment arrangements (shares)			120,119
Tax withholding related to share-based compensation				(13,797)
Shares issued for Employee Stock Purchase Plan (value)			$ 1	6,658
Shares issued for Employee Stock Purchase Plan (shares)			56,208
Stock-based compensation expense				8,651
Net Income	210,892				210,892
Dividends (value)					(87,970)
Purchase of treasury shares						(21,276)
Balance, end of period (value) at Mar. 31, 2019	$ 1,426,003		$ 1,035	465,649	2,035,855	(1,076,536)
Shares, end of period at Mar. 31, 2019			103,454,889
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share	$ 1.14
Cumulative Effect of New Accounting Principle in Period of Adoption					0
Balance, beginning of period (value) at Dec. 31, 2018			$ 1,034	459,988	2,007,469	(1,076,536)
Shares, beginning of period at Dec. 31, 2018			103,428,416
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for equity-based payment arrangements (value)			$ 0	0
Shares issued for equity-based payment arrangements (shares)			4,722
Tax withholding related to share-based compensation				(313)
Shares issued for Employee Stock Purchase Plan (value)			$ 1	2,469
Shares issued for Employee Stock Purchase Plan (shares)			21,751
Stock-based compensation expense				3,505
Net Income	$ 59,252				59,252
Dividends (value)					(30,866)
Purchase of treasury shares						0
Balance, end of period (value) at Mar. 31, 2019	$ 1,426,003		$ 1,035	$ 465,649	$ 2,035,855	$ (1,076,536)
Shares, end of period at Mar. 31, 2019			103,454,889
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per share	$ 0.40
Preferred Shares		0