Revenue from External Customers and Asset, by Geographical Areas (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2014	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Assets						$ 3,271,197	$ 3,018,175	$ 2,859,085
Revenues	764,363	768,426	828,473	1,596,899	2,361,262	3,157,796	3,094,018	3,075,671
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Assets						3,204,283	2,940,980	2,794,883
Revenues						3,075,387	3,035,558	3,035,556
Mexico [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Assets						59,841	69,826	46,038
Revenues						72,202	47,171	22,502
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Assets						7,073	7,369	18,164
Revenues						$ 10,207	$ 11,289	$ 17,613