Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2012	$ 1,455,857	$ 1,085	$ 784,725	$ 1,798,287	$ (1,130,268)	$ 2,028
Balance, shares at Dec. 31, 2012		108,531,000
Net earnings	128,757			128,757
Other comprehensive income (loss)	(2,017)					(2,017)
Purchase of treasury stock	(217,421)		(12)		(217,409)
Exercise of stock options, shares		479,000
Exercise of stock options	11,932	$ 5	11,927
Vesting of restricted share units, shares		98,000
Vesting of restricted share units	1	$ 1
Tax effects of stock awards vested and options exercised	(972)		(972)
Stock-based compensation	6,456		6,456
Dividends declared	(46,724)			(46,724)
Balance at Dec. 31, 2013	1,335,869	$ 1,091	802,124	1,880,320	(1,347,677)	11
Balance, shares at Dec. 31, 2013		109,108,000
Net earnings	96,422			96,422
Other comprehensive income (loss)	(4,656)					(4,656)
Exercise of stock options, shares		212,000
Exercise of stock options	4,647	$ 2	4,645
Vesting of restricted share units, shares		33,000
Vesting of restricted share units	1	$ 1
Tax effects of stock awards vested and options exercised	(150)		(150)
Stock-based compensation	6,559		6,559
Dividends declared	(49,297)			(49,297)
Balance at Dec. 31, 2014	1,389,395	$ 1,094	813,178	1,927,445	(1,347,677)	(4,645)
Balance, shares at Dec. 31, 2014		109,353,000
Net earnings	(866,628)			(866,628)
Other comprehensive income (loss)	$ (6,399)					(6,399)
Exercise of stock options, shares	65,366	66,000
Exercise of stock options	$ 1,485		1,485
Vesting of restricted share units, shares		23,000
Tax effects of stock awards vested and options exercised	(5,865)		(5,865)
Stock-based compensation	9,541		9,541
Dividends declared	(51,047)			(51,047)
Balance at Dec. 31, 2015	$ 470,482	$ 1,094	$ 818,339	$ 1,009,770	$ (1,347,677)	$ (11,044)
Balance, shares at Dec. 31, 2015		109,442,000