Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Income tax expense	$ 25,292	$ 10,681	$ 56,353	$ 29,035
Effective tax rates (percent)	36.60%	22.10%	36.20%	28.40%
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions					$ 6,449