Consolidated Statement of Operations (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Income from discontinued operations, tax	$ 24,495	$ 39,561	$ 22,366

Amount of tax expense (benefit) attributable to income (loss) from operations classified as a discontinued operation. Excludes tax expense (benefit) for gain (loss) on disposal and for provision for gain (loss) until disposal.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration