Stockholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended		12 Months Ended					12 Months Ended																12 Months Ended				12 Months Ended					1 Months Ended	12 Months Ended
	Jan. 31, 2012	Jun. 30, 2009	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	May 31, 2010 Minimum	May 31, 2011 Maximum	Dec. 31, 2011 Restricted Stock Units (RSUs) Y	Dec. 31, 2010 Restricted Stock Units (RSUs)	Dec. 31, 2009 Restricted Stock Units (RSUs)	Dec. 31, 2011 Stock Appreciation Rights (SARs) Y	Dec. 31, 2010 Stock Appreciation Rights (SARs)	Dec. 31, 2009 Stock Appreciation Rights (SARs)	Dec. 31, 2011 Nonvested stock units issued (NSUs) Y	Dec. 31, 2010 Nonvested stock units issued (NSUs)	Dec. 31, 2009 Nonvested stock units issued (NSUs)	Dec. 31, 2011 Directors' shares	Dec. 31, 2010 Directors' shares	Dec. 31, 2009 Directors' shares	Dec. 31, 2011 2006 Equity Incentive Plan (2006 Plan)	Dec. 31, 2011 2006 Equity Incentive Plan (2006 Plan) Restricted Stock Units (RSUs)	Dec. 31, 2010 2006 Equity Incentive Plan (2006 Plan) Restricted Stock Units (RSUs)	Dec. 31, 2008 2006 Equity Incentive Plan (2006 Plan) Restricted Stock Units (RSUs)	Dec. 31, 2011 2006 Equity Incentive Plan (2006 Plan) Stock Appreciation Rights (SARs) Y	Dec. 31, 2010 2006 Equity Incentive Plan (2006 Plan) Stock Appreciation Rights (SARs) Y	Dec. 31, 2009 2006 Equity Incentive Plan (2006 Plan) Stock Appreciation Rights (SARs) Y	Dec. 31, 2008 2006 Equity Incentive Plan (2006 Plan) Stock Appreciation Rights (SARs) Y	Dec. 31, 2011 2006 Equity Incentive Plan (2006 Plan) Nonvested stock units issued (NSUs)	Dec. 31, 2010 2006 Equity Incentive Plan (2006 Plan) Nonvested stock units issued (NSUs)	Dec. 31, 2009 2006 Equity Incentive Plan (2006 Plan) Nonvested stock units issued (NSUs)	Dec. 31, 2011 Long-term incentive award SAR awards and RSU awards	Dec. 31, 2011 Long-term incentive award (Level III Awards)	Jun. 30, 2011 Long-term incentive award (Level III Awards) Restricted Stock Units (RSUs)	Dec. 31, 2011 Long-term incentive award (Level III Awards) Restricted Stock Units (RSUs) Maximum
Stock Repurchased During Period, Value			$ 19,918	$ 10,082	$ 20,000
Stockholders' equity
Common stock reserved for issuance (in shares)																				6,000,000
Maximum number of shares that may be issued through the exercise of incentive stock options																				4,500,000
Quarterly vesting rights from the anniversary of the grants																				between the third and fourth anniversary of the grant
Portion of SAR and RSU awards scheduled to vest on December 31, 2010 and December 31, 2011																															one-half
Portion of SAR and RSU awards scheduled to vest on December 31, 2015 and December 31, 2016																															one-half
Percentage of portion of SAR and RSU awards scheduled to vest on December 31, 2010																															80.00%
Percentage of portion of SAR and RSU awards scheduled to vest on December 31, 2011																															20.00%
Percentage of portion of SAR and RSU awards scheduled to vest on December 31, 2015																															80.00%
Percentage of portion of SAR and RSU awards scheduled to vest on December 31, 2016																															20.00%
Maximum contractual term of SARs with final vesting date of December 31, 2011 (in years)											10
Maximum contractual term of SARs with final vesting date of December 31, 2016 (in years)											15
Authorized number of shares of common stock (in shares)			125,000,000	125,000,000		50,000,000	125,000,000
Maximum stock repurchase amount approved by Board of Directors	100,000	50,000
Number of shares repurchased			245,000	230,000	900,000
Repurchase of common stock, payments			19,918	10,082	20,000
Average stock price of shares repurchased (in dollars per share)			$ 81.22	$ 43.67	$ 22.14
Number of shares receivable as right under stock-based awards																																	1
Number of shares granted																					275,000							199,000	315,000	291,000				275,000
Grant date fair value of awards (in dollars per share)																					$ 82.09							$ 87.50	$ 45.99	$ 17.80
Compensation expense cumulative amount based on maximum number of units subject to performance objectives probable																																2,740
Stock compensation expenses
Compensation expenses recorded			14,803	12,782	13,016			305	677	994	1,813	3,420	5,287	11,719	7,915	5,652	966	770	1,083
Income tax benefit recognized			(5,788)	(5,127)	(5,096)
Net compensation expenses			9,015	7,655	7,920
Unrecognized Compensation Cost			26,178					981			6,384			18,813
Weighted-Average Remaining Vesting Period (in years)								4.2			4.2			1.4
Maximum compensation cost excluded from unrecognized compensation cost subject to performance condition not considered probable																																20,591
Nonvested Stock Units and Restricted Stock Units Issued Under the 2006 Plan
Nonvested at the beginning of the period (in shares)																					85,000	159,000	159,000	1,125,000	1,200,000		1,200,000	798,000	717,000	744,000
Granted (in shares)																					275,000							199,000	315,000	291,000				275,000
Vested (in shares)																					(16,000)	(64,000)						(263,000)	(208,000)	(288,000)
Forfeited (in shares)																					(25,000)	(10,000)			(75,000)			(57,000)	(26,000)	(30,000)
Nonvested at the end of the period (in shares)																					319,000	85,000	159,000	760,000	1,125,000		1,200,000	677,000	798,000	717,000
Weighted-Average Grant-Date Fair Value
Nonvested at the beginning of the period (in dollars per share)																					$ 26.73	$ 26.73	$ 26.73					$ 35.61	$ 26.34	$ 23.52
Granted (in dollars per share)																					$ 82.09							$ 87.50	$ 45.99	$ 17.80
Vested (in dollars per share)																					$ 26.73	$ 26.73						$ 40.31	$ 22.83	$ 10.42
Forfeited (in dollars per share)																					$ 82.09	$ 26.73						$ 46.61	$ 25.98	$ 26.34
Nonvested at the end of the period (in dollars per share)																					$ 70.15	$ 26.73	$ 26.73					$ 48.14	$ 35.61	$ 26.34
Expected to vest at the end of the period (in dollars per share)																					$ 26.73
Stock Appreciation Rights Issued Under the 2006 Plan
Nonvested at the beginning of the period (in shares)																					85,000	159,000	159,000	1,125,000	1,200,000		1,200,000	798,000	717,000	744,000
Granted (in shares)																					275,000							199,000	315,000	291,000				275,000
Exercised (in shares)																								(365,000)
Forfeited (in shares)																					(25,000)	(10,000)			(75,000)			(57,000)	(26,000)	(30,000)
Nonvested at the end of the period (in shares)																					319,000	85,000	159,000	760,000	1,125,000		1,200,000	677,000	798,000	717,000
Exercisable at the end of the period (in shares)																								115,000
Expected to vest and exercisable (in shares)																								704,000
Stock appreciation rights exercisable during period (in shares)																								120,000
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)																								$ 26.73	$ 26.73		$ 26.73
Forfeited (in dollars per share)																									$ (26.73)
Exercised (in dollars per share)																									$ 26.73
Outstanding at the end of the period (in dollars per share)																								$ 26.73	$ 26.73		$ 26.73
Exercisable at the end of the period (in dollars per share)																								$ 26.73
Expected to vest and exercisable (in dollars per share)																								$ 26.73
Weighted-Average Remaining Contractual Term
Outstanding at the end of the period (in years)																								8.8	8.7	9.8	10.8
Exercisable at the end of the period (in years)																								5.4
Expected to vest and exercisable (in years)																								8.7
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)																								37,118	59,636	8,608
Exercisable at the end of the period (in dollars)																								5,617
Expected to vest and exercisable (in dollars)																								$ 34,381
Shares issued																																16,000