Income Taxes - Additional Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Tax Disclosure [Abstract]
Income tax expense	$ 143,643	$ 104,129	$ 191,684	$ 256,927
Effective tax rate	36.80%	36.50%	36.90%	35.30%