Stock-Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock-based compensation costs - expensed	$ 5,427,000	$ 4,959,000	$ 4,706,000
Stock-based compensation costs - capitalized	4,468,000	3,365,000	2,679,000
Unrecognized compensation cost related to unvested stock option and restricted stock grants	20,400,000
Weighted average period over which cost is recognized, years	2 years 10 months 29 days
Stock options, Outstanding at January 1, Number of options	4,741,732	4,769,122	5,649,233
Stock options, Granted, Number of options	613,120	853,478	446,895
Stock options, Exercised, Number of options	(1,607,784)	(850,659)	(1,293,046)
Stock options, Forfeited or expired, Number of options	(97,548)	(30,209)	(33,960)
Stock options, Outstanding at December 31, Number of options	3,649,520	4,741,732	4,769,122
Stock options, Outstanding at January 1, Weighted average exercise price	$ 21.24	$ 16.13	$ 11.59
Stock options, Granted, Weighted average exercise price	$ 34.34	$ 36.64	$ 37.05
Stock options, Exercised, Weighted average exercise price	$ 5.71	$ 7.54	$ 3.01
Stock options, Forfeited or expired, Weighted average exercise price	$ 37.76	$ 35.46	$ 35.26
Stock options, Outstanding at December 31, Weighted average exercise price	$ 29.84	$ 21.24	$ 16.13
2004 Plan [Member]
Maximum shares	16,800,000
2002 Plan [Member]
Maximum shares	300,000
2000 Plan [Member]
Maximum shares	1,250,000
Stock Options [Member]
Deferred tax benefit (liability) recorded	2,200,000	1,700,000	1,700,000
Stock options, Outstanding at December 31, Number of options	3,649,520
Stock options, Outstanding at December 31, Weighted average exercise price	$ 29.84
Weighted-average grant-date fair value of options granted	$ 16.91	$ 18.17	$ 19.40
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value	44,100,000	27,000,000	41,400,000
Restricted Stock [Member]
Stock-based compensation costs - expensed	6,368,000	5,591,000	5,114,000
Stock-based compensation costs - capitalized	5,994,000	5,162,000	4,107,000
Deferred tax benefit (liability) recorded	1,400,000	2,100,000	1,400,000
Weighted-average grant-date fair value of options granted	$ 34.39	$ 36.41	$ 36.46
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Share-based Awards Other than Options	32,000,000
Weighted average period over which cost is recognized, restricted stock (years)	3 years 2 months 13 days
Total fair value of restricted stock grants	18,500,000	19,400,000	14,200,000
Total fair value of shares vested	$ 12,600,000	$ 10,900,000	$ 9,700,000