General - Basis of Presentation (Details 2) (USD $)	1 Months Ended	3 Months Ended				3 Months Ended			3 Months Ended
	Jun. 30, 2011	Mar. 31, 2013	Mar. 31, 2013 Long-Term Incentive Plan	Mar. 31, 2012 Long-Term Incentive Plan	May 31, 2012 Long-Term Incentive Plan	Mar. 31, 2013 Long-Term Incentive Plan Stock options installment	Mar. 31, 2012 Long-Term Incentive Plan Stock options	Mar. 31, 2013 Long-Term Incentive Plan Restricted stock and restricted stock units	Mar. 31, 2013 Long-Term Incentive Plan Stock, restricted stock awards and restricted stock units	Dec. 31, 2012 Long-Term Incentive Plan Stock, restricted stock awards and restricted stock units
Details of stock benefit plans
Number of shares of common stock that may be issued under the Plan					9,666,666
Stock split ratio	2
Maximum number of shares of common stock authorized to be issued under the Plan			14,066,666
Stock-based compensation expense		$ 7,097,000	$ 7,000,000	$ 16,900,000
Options to purchase common stock outstanding (in shares)						4,728,000		346,000
Shares outstanding under the plan									346,000	347,000
Shares available for future grant			3,039,000
Number of equal annual installments over which options outstanding are cumulatively exercisable						4
Options exercisable commencement period from grant date						1 year
Term over which options are granted						10 years
Portion of expected volatility based on historical volatility of similar entities' common stock (as a percent)						0.67
Portion of expected volatility based on historical volatility of the entity's common stock (as a percent)						0.33
Weighted-average assumptions used to estimate the fair value of stock options granted
Risk-free interest rate (as a percent)						1.20%	1.23%
Expected term						6 years 3 months	6 years 3 months
Expected volatility (as a percent)						39.22%	44.20%
Expected dividend yield (as a percent)						5.26%	4.60%
Shares
Options outstanding at the beginning of the period (in shares)						4,718,000		346,000
Granted (in shares)						131,000
Exercised (in shares)						(83,000)
Forfeited (in shares)						(38,000)
Options outstanding at the end of the period (in shares)						4,728,000		346,000
Vested and expected to vest (in shares)						4,582,000
Options exercisable (in shares)						370,000
Weighted Avg. Exercise Price (in dollars per share)
Options outstanding at the beginning of the period (in dollars per share)						$ 30.07
Granted (in dollars per share)						$ 66.68
Exercised (in dollars per share)						$ 30.07
Forfeited (in dollars per share)						$ 35.30
Options outstanding at the end of the period (in dollars per share)						$ 31.04
Vested and expected to vest (in dollars per share)						$ 30.99
Options exercisable (in dollars per share)						$ 24.78
Weighted Avg. Remaining Contractual Term
Options outstanding at the end of the period						8 years 1 month 6 days
Vested and expected to vest						8 years 1 month 6 days
Options exercisable						7 years 8 months 23 days
Aggregate Intrinsic Value (in dollars)
Options outstanding at the end of the period (in dollars)						195,898,000
Vested and expected to vest (in dollars)						190,100,000
Options exercisable (in dollars)						17,673,000
Stock-based compensation additional disclosures
Weighted average grant date fair value of options granted (in dollars per share)						$ 14.35	$ 12.60
Total intrinsic value of options exercised (in dollars)						3,200,000	12,500,000
Fair value of options vested during the period (in dollars)						900,000	700,000
Unrecognized compensation expense (in dollars)						17,300,000			1,600,000
Weighted-average period over which unrecognized compensation cost is expected to be recognized						2 years 9 months 14 days			1 year 4 months 20 days
Cash received from the exercise of stock option						$ 2,500,000	$ 8,400,000