Stockholders' Equity (Details) (USD $)	1 Months Ended		6 Months Ended	12 Months Ended																12 Months Ended											1 Months Ended				12 Months Ended					1 Months Ended				1 Months Ended			12 Months Ended
	Jun. 30, 2012	Feb. 29, 2012	Jun. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Nonvested stock units issued (NSUs)	Dec. 31, 2012 Nonvested stock units issued (NSUs)	Dec. 31, 2011 Nonvested stock units issued (NSUs)	Dec. 31, 2013 Restricted Stock Units (RSUs)	Dec. 31, 2012 Restricted Stock Units (RSUs)	Dec. 31, 2011 Restricted Stock Units (RSUs)	Dec. 31, 2013 Directors' shares	Dec. 31, 2012 Directors' shares	Dec. 31, 2011 Directors' shares	Dec. 31, 2013 Stock Appreciation Rights (SARs)	Dec. 31, 2012 Stock Appreciation Rights (SARs)	Dec. 31, 2011 Stock Appreciation Rights (SARs)	Dec. 31, 2013 2006 Equity Incentive Plan (2006 Plan)	Dec. 31, 2013 2006 Equity Incentive Plan (2006 Plan) Nonvested stock units issued (NSUs)	Dec. 31, 2012 2006 Equity Incentive Plan (2006 Plan) Nonvested stock units issued (NSUs)	Dec. 31, 2011 2006 Equity Incentive Plan (2006 Plan) Nonvested stock units issued (NSUs)	Dec. 31, 2013 2006 Equity Incentive Plan (2006 Plan) Nonvested stock units issued (NSUs) Award granted in 2011	Dec. 31, 2013 2006 Equity Incentive Plan (2006 Plan) Restricted Stock Units (RSUs)	Dec. 31, 2012 2006 Equity Incentive Plan (2006 Plan) Restricted Stock Units (RSUs)	Dec. 31, 2011 2006 Equity Incentive Plan (2006 Plan) Restricted Stock Units (RSUs)	Dec. 31, 2013 2006 Equity Incentive Plan (2006 Plan) Stock Appreciation Rights (SARs)	Dec. 31, 2012 2006 Equity Incentive Plan (2006 Plan) Stock Appreciation Rights (SARs)	Dec. 31, 2011 2006 Equity Incentive Plan (2006 Plan) Stock Appreciation Rights (SARs)	Dec. 31, 2010 2006 Equity Incentive Plan (2006 Plan) Stock Appreciation Rights (SARs)	Dec. 31, 2013 Long-term incentive awards group	May 31, 2012 Long-term incentive awards Maximum	May 31, 2012 Long-term incentive awards Minimum	May 31, 2012 Long-term incentive awards Restricted Stock Units (RSUs)	Dec. 31, 2013 Long-term incentive awards Restricted Stock Units (RSUs)	Dec. 31, 2012 Long-term incentive awards Restricted Stock Units (RSUs)	Dec. 31, 2013 Long-term incentive awards Restricted Stock Units (RSUs) Maximum	Dec. 31, 2012 Long-term incentive awards Restricted Stock Units (RSUs) Maximum	Dec. 31, 2013 Long-term incentive awards SAR awards and RSU awards	Dec. 31, 2013 Non-revenue Generating Group Maximum	Dec. 31, 2013 Non-revenue Generating Group Minimum	Dec. 31, 2013 Revenue Generating Group Minimum	Dec. 31, 2013 Long-term incentive award (Level III Awards)	Jun. 30, 2011 Long-term incentive award (Level III Awards) Maximum	Jun. 30, 2011 Long-term incentive award (Level III Awards) Minimum	Jun. 30, 2011 Long-term incentive award (Level III Awards) Restricted Stock Units (RSUs)	Dec. 31, 2012 Long-term incentive award (Level III Awards) Restricted Stock Units (RSUs)	Dec. 31, 2012 Long-term incentive award (Level III Awards) Restricted Stock Units (RSUs) Maximum
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
Awards granted that will vest after the performance goals are achieved (as a percent)																							33.33%
Award vesting period																							3 years
Portion of SAR and RSU awards scheduled to vest on December 31, 2010 and December 31, 2011																																							50.00%
Portion of SAR and RSU awards scheduled to vest on December 31, 2015 and December 31, 2016																																							50.00%
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%
Number of shares receivable as right under stock-based awards																																		1												1
Revenue targets to be met for awards to be vested																																$ 2,900,000,000	$ 2,200,000,000							$ 2,558,000,000	$ 2,290,000,000			$ 2,500,000,000	$ 1,850,000,000
Diluted earnings per share targets to be met for awards to be vested (in dollars per share)																																$ 10.50	$ 7.00											$ 9.60	$ 7.00
Number of shares granted																				304,000	209,000	199,000		156,000	352,000	275,000											156,000	352,000										275,000
Grant date fair value of RSUs																				$ 57.30	$ 63.18	$ 87.50		$ 84.52	$ 56.12	$ 82.09									$ 84.52	$ 56.12											$ 82.09
Compensation expense cumulative amount based on maximum number of units subject to performance objectives probable																															8,000,000												14,000,000
Number of participant groups																															2
EBITDA targets to be met for awards to be vested																																								415,000,000	372,000,000	350,000,000
Maximum stock repurchase amount approved by Board of Directors	200,000,000	100,000,000
Number of shares repurchased			1,749,000	2,765,000
Repurchase of common stock, payments			100,000,000	120,700,000
Average stock price of shares repurchased (in dollars per share)			$ 57.16	$ 43.66
Remaining stock repurchase amount approved by Board of Directors				79,300,000
Maximum contractual term of SARs with final vesting date of December 31, 2011 (in years)																	10 years
Maximum contractual term of SARs with final vesting date of December 31, 2016 (in years)																	15 years
Stock appreciation rights exercisable during period (in shares)																												120,000
Stock compensation expenses
Compensation expenses recorded				13,136,000	14,661,000	14,803,000	10,545,000	11,849,000	11,719,000	287,000	231,000	305,000	1,002,000	1,080,000	966,000	1,302,000	1,501,000	1,813,000
Income tax benefit recognized				(4,950,000)	(5,573,000)	(5,788,000)
Net compensation expenses				8,186,000	9,088,000	9,015,000
Unrecognized Compensation Cost				20,868,000			12,427,000			4,859,000						3,582,000
Weighted-Average Remaining Vesting Period (in years)							1 year 9 months 18 days			2 years 2 months 12 days						2 years 2 months 12 days
Maximum compensation cost excluded from unrecognized compensation cost subject to performance condition not considered probable																															18,445,000												19,825,000
Nonvested Stock Units and Restricted Stock Units Issued Under the 2006 Plan
Nonvested at the beginning of the period (in shares)																				371,000	677,000	798,000		671,000	319,000	85,000	745,000	760,000	1,125,000
Granted (in shares)																				304,000	209,000	199,000		156,000	352,000	275,000											156,000	352,000										275,000
Vested (in shares)																				(315,000)	(297,000)	(263,000)		0	0	(16,000)
Forfeited (in shares)																				(20,000)	(18,000)	(57,000)		(32,000)	0	(25,000)			0
Cancelled (in shares)																					(200,000)
Nonvested at the end of the period (in shares)																				340,000	371,000	677,000		795,000	671,000	319,000	730,000	745,000	760,000	1,125,000
Weighted-Average Grant-Date Fair Value
Nonvested at the beginning of the period (in dollars per share)																				$ 58.51	$ 48.14	$ 35.61		$ 62.80	$ 70.15	$ 26.73
Granted (in dollars per share)																				$ 57.30	$ 63.18	$ 87.50		$ 84.52	$ 56.12	$ 82.09									$ 84.52	$ 56.12											$ 82.09
Vested (in dollars per share)																				$ 53.19	$ 35.90	$ 40.31		$ 0.00	$ 0.00	$ 26.73
Forfeited (in dollars per share)																				$ 61.08	$ 63.68	$ 46.61		$ 63.69	$ 0.00	$ 82.09
Cancelled (in dollars per share)																					$ 62.17
Nonvested at the end of the period (in dollars per share)																				$ 62.23	$ 58.51	$ 48.14		$ 67.03	$ 62.80	$ 70.15
Stock Appreciation Rights Issued Under the 2006 Plan
Nonvested at the beginning of the period (in shares)																				371,000	677,000	798,000		671,000	319,000	85,000	745,000	760,000	1,125,000
Granted (in shares)																				304,000	209,000	199,000		156,000	352,000	275,000											156,000	352,000										275,000
Exercised (in shares)																											(15,000)	(15,000)	(365,000)
Forfeited (in shares)																				(20,000)	(18,000)	(57,000)		(32,000)	0	(25,000)			0
Nonvested at the end of the period (in shares)																				340,000	371,000	677,000		795,000	671,000	319,000	730,000	745,000	760,000	1,125,000
Exercisable at the end of the period (in shares)																											205,000
Expected to vest and exercisable (in shares)																											694,817
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)																											$ 26.73	$ 26.73	$ 26.73
Exercised (in dollars per share)																											$ 26.73	$ 26.73	$ 26.73
Forfeited (in dollars per share)																													$ 0.00
Outstanding at the end of the period (in dollars per share)																											$ 26.73	$ 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 (in years)
Outstanding at the end of the period (in years)																											6 years 11 months 12 days	7 years 10 months 17 days	8 years 9 months 18 days	8 years 8 months 12 days
Exercisable at the end of the period (in years)																											3 years 4 months 10 days
Expected to vest and exercisable (in years)																											6 years 10 months 17 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)																											42,143,000	10,087,000	37,118,000	59,636,000
Exercisable at the end of the period (in dollars)																											11,835,000
Expected to vest and exercisable (in dollars)																											$ 40,112,000