Shareholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended						1 Months Ended	6 Months Ended		0 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jul. 31, 2013 Minimum	Jul. 31, 2013 Maximum	Jul. 31, 2014 Subsequent Event Minimum	Jul. 31, 2014 Subsequent Event Maximum	Jan. 31, 2013 2013 Stock Repurchase Program	Jun. 30, 2014 2013 Stock Repurchase Program	Jul. 31, 2014 2013 Stock Repurchase Program	Jul. 31, 2014 2013 Stock Repurchase Program Subsequent Event
Number of shares authorized to be repurchased under the current open-market stock repurchase program									10,000,000		2,743,060
Repurchase of stock program, period									2 years
Number of shares repurchased under the current open-market stock repurchase program										2,765,797		205,448
Payments for shares repurchased under the current open-market stock repurchase program (in dollars)										$ 250,159		$ 19,996
Quarterly dividend approved by Board prior to payment, per share (in dollars per share)					$ 0.105	$ 0.20	$ 0.20	$ 0.25
Dividends paid	31,418	16,756	31,418	16,756
Dividends declared	$ 31,370	$ 16,713	$ 62,788	$ 33,468