Consolidated Statements of Changes in Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest
Beginning Balance at Dec. 31, 2012	$ 973,656	$ 126,544	$ 187,394	$ 658,994	$ (406)	$ 1,130
Beginning Balance (in shares) at Dec. 31, 2012		63,271
Net income	54,970			54,970
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income	(5,752)				(5,752)
Dividends declared	(30,324)			(30,324)
Shares repurchased and retired (in shares)		(257)
Shares repurchased and retired	(8,297)	(515)		(7,782)
Share-based compensation expense, exercises and other (shares)		319
Share-based compensation expense, exercises and other	5,568	636	4,932
Ending Balance at Jun. 30, 2013	989,821	126,665	192,326	675,858	(6,158)	1,130
Ending Balance (in shares) at Jun. 30, 2013		63,333
Beginning Balance at Dec. 31, 2013	1,025,043	126,193	196,605	691,547	9,568	1,130
Beginning Balance (in shares) at Dec. 31, 2013	63,096	63,096
Net income	45,362			45,362
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income	122				122
Dividends declared	(31,473)			(31,473)
Shares repurchased and retired (in shares)	(277)	(277)
Shares repurchased and retired	(9,448)	(555)		(8,893)
Share-based compensation expense, exercises and other (shares)		247
Share-based compensation expense, exercises and other	3,604	495	3,109
Purchase of noncontrolling interest	(1,825)		(695)			(1,130)
Ending Balance at Jun. 30, 2014	$ 1,031,385	$ 126,133	$ 199,019	$ 696,543	$ 9,690	$ 0
Ending Balance (in shares) at Jun. 30, 2014	63,066	63,066