Consolidated Statement of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Income Tax Expense (Benefit)	$ (46,063)	$ 14,162	$ 11,884
Additional Paid-in Capital [Member]
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	$ 0	$ 2,142	$ 1,841