Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Treasury stock, shares of common stock (in shares)	1,353	2,064	1,448
Retirement of treasury shares (in shares)	(1,353)	(2,064)	(1,448)
Interest rate swap, tax	$ (769)	$ (839)	$ 653
Exercise and lapse of share-based awards, tax benefit	$ 0	$ 7,370	$ 7,706