Fair Value Measurements (Details Textual) - USD ($) $ in Thousands	Dec. 31, 2016	Apr. 02, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	$ 3,374,965	$ 3,492,322
Senior Notes [Member] | 2.125% 2019 Senior Debentures [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debentures	500,800
Senior Notes [Member] | 3.0% 2021 Senior Debentures [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debentures	506,000
Convertible Notes [Member] | Two And Six Two Five Percent Senior Convertible Debentures [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debentures	$ 1,250,000