Balance Sheet Parenthetical (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Available-for-sale Debt Securities, Amortized Cost Basis	$ 2,941,528	$ 2,856,468
Available-for-sale Equity Securities, Amortized Cost Basis	$ 1,330	$ 1,330
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common Stock, Par or Stated Value Per Share	$ 0.001	$ 0.001
Common Stock, Shares Authorized	485,000,000	485,000,000
Common Stock, Shares, Issued	232,663,818	232,091,921
Common Stock, Shares, Outstanding	215,090,781	214,521,079
Treasury Stock, Shares	17,573,037	17,570,842