Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended			24 Months Ended
	Aug. 05, 2015	May. 11, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014
Equity, Class of Treasury Stock [Line Items]
Marketable securities unrealized gain (loss), net of tax			$ (57,117)	$ 71,959	$ (254)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax			(31,468)	39,676	(136)
Stock Repurchased During Period, Value			$ 103,874	$ 1,343	$ 46,052
Shares purchased during period, shares			4,015,866	62,909	966,700
Average price paid per share			$ 25.87	$ 21.35	$ 47.64
Gain on disposition of equity securities			$ 1,688	$ 0	$ 0
Income Tax Expense (Benefit)			15,478	2,041	(15,505)
Accumulated Other Comprehensive Income [Member]
Equity, Class of Treasury Stock [Line Items]
Marketable securities unrealized gain (loss), net of tax			(57,117)	$ 71,959	$ (254)
Marketable securities, net of tax
Equity, Class of Treasury Stock [Line Items]
Income Tax Expense (Benefit)			$ 600
2013 Authorization [Member]
Equity, Class of Treasury Stock [Line Items]
Shares purchased during period, shares						1,029,609
ASR [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased During Period, Value		$ 18,700
Shares purchased during period, shares		684,230	829,666
Adjustments to additional paid in capital, Accelerated share repurchases	$ 3,300
Accelerated Share Repurchases, Initial Cash Paid		$ 22,000
Accelerated Share Repurchase Program Shares Adjustment	145,436
Maximum [Member] | 2013 Authorization [Member]
Equity, Class of Treasury Stock [Line Items]
Board of Directors authorized to purchase shares			2,500,000.0
Maximum [Member] | January 2015 Authorization [Member]
Equity, Class of Treasury Stock [Line Items]
Board of Directors authorized to purchase shares			4,000,000
Maximum [Member] | October 2015 Authorization [Member]
Equity, Class of Treasury Stock [Line Items]
Board of Directors authorized to purchase shares			3,000,000.0
Enova [Member] | Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax			$ (88,600)
Marketable securities unrealized gain (loss), net of tax			$ 23,000