Reclassification out of accumulated other comprehensive income (loss) (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Interest expense	$ (22,946)	$ (22,402)	$ (69,864)	$ (64,832)
Other income	3,498	2,524	6,261	7,162
Income taxes	(36,895)	(35,376)	(52,520)	(63,072)
Income from continuing operations	53,400	63,639	82,618	124,113
Income (loss) from discontinued operations, net of tax	(202,626)	38,482	(778,647)	87,475
Net income (loss)	(149,226)	102,121	(696,029)	211,588
Reclassification from accumulated other comprehensive income, current period, net of tax	(510)	(374)	(2,540)	(1,320)
Accumulated net gain (loss) from cash flow hedges including portion attributable to noncontrolling interest [Member] | Reclassification out of accumulated other comprehensive income [Member]
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Net income (loss)	(100)	(82)	(299)	(439)
Accumulated net gain (loss) from cash flow hedges including portion attributable to noncontrolling interest [Member] | Reclassification out of accumulated other comprehensive income [Member] | Interest rate contract [Member]
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Interest expense	(160)	(160)	(480)	(480)
Income taxes	60	60	181	181
Income from continuing operations	(100)	(100)	(299)	(299)
Accumulated net gain (loss) from cash flow hedges including portion attributable to noncontrolling interest [Member] | Reclassification out of accumulated other comprehensive income [Member] | Commodity contract [Member]
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Income (loss) from discontinued operations, net of tax	0	18	0	(140)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Reclassification from accumulated other comprehensive income	(615)	(420)	(2,222)	(1,258)
Reclassification from AOCI, current period, tax	233	159	881	477
Reclassification from accumulated other comprehensive income, current period, net of tax	(382)	(261)	(1,341)	(781)
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member] | Reclassification out of accumulated other comprehensive income [Member]
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Other income	0	0	(1,293)	0
Income taxes	0	0	491	0
Net income (loss)	0	0	(802)	0
Accumulated net investment gain (loss) including portion attributable to noncontrolling interest [Member] | Reclassification out of accumulated other comprehensive income [Member]
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Other income	(43)	(47)	(151)	(154)
Income taxes	15	16	53	54
Net income (loss)	$ (28)	$ (31)	$ (98)	$ (100)