Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Effective income tax rate (as a percent)	38.10%		42.00%	41.30%	42.40%
Discrete tax expense due to change in tax laws	$ 300			$ 300
Discrete tax rate changes due to change in tax laws (as a percent)	2.80%			1.10%
Excess tax benefit from exercise of stock options	$ 21,000			$ 1,477
Tax deductions arising from stock-based compensation				4,000
Net unrecognized tax benefits	1,100		$ 1,600	1,100	$ 1,600
Accrued liabilities for interest expense and penalties related to unrecognized tax benefits	$ 400		$ 300	$ 400	$ 300
State and Local Jurisdiction [Member]
Discrete tax expense due to change in tax laws		$ 600
Discrete tax rate changes due to change in tax laws (as a percent)	0.00%			1.30%