Stock-Based Compensation--2010 Equity Incentive Plan (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Vest date fair value
Restricted stock used for tax withholding	1,068
Maximum | Time Vested | 2010 Equity Incentive Plan | Restricted Stock
Stock-Based Compensation [Line Items]
Award vesting period	5 years
Common Class A
Vest date fair value
Restricted stock used for tax withholding	1,068
Common Class A | 2010 Equity Incentive Plan | Restricted Stock
Stock-Based Compensation [Line Items]
Shares reserved for issuance under the 2010 Plan	86,301
Common Class A | Time Vested | 2010 Equity Incentive Plan | Restricted Stock
Weighted average grant date fair value ($ per share)
Unvested and outstanding at beginning of period	$ 634.67
Granted	$ 818.50
Vested	$ 633.14
Unvested and outstanding at end of period	$ 651.27
Shares
Unvested and outstanding at beginning of period (in shares)	19,246
Granted (in shares)	1,615
Vested (in shares)	(2,721)
Unvested and outstanding at end of period (in shares)	18,140
Vest date fair value
Vest date fair value	$ 2,227
Restricted stock used for tax withholding	1,068	123
Shares expected to be repurchased during the next twelve months	2,000
Estimated fair value per share at end of period	$ 818.50
Aggregate intrinsic value of unvested Time Vested restricted shares outstanding	$ 14,848
Common Class A | Performance Vested | 2010 Equity Incentive Plan | Restricted Stock
Weighted average grant date fair value ($ per share)
Unvested and outstanding at beginning of period	$ 307.45
Granted	$ 204.90
Vested	$ 0.00
Unvested and outstanding at end of period	$ 301.26
Shares
Unvested and outstanding at beginning of period (in shares)	46,701
Granted (in shares)	2,998
Vested (in shares)	0
Unvested and outstanding at end of period (in shares)	49,699