Segment Reporting (Geographic Data) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenue	$ 1,440,727	$ 1,504,150	$ 1,492,349	$ 1,368,843	$ 1,357,801	$ 1,398,021	$ 1,381,370	$ 1,336,164	$ 5,806,069	$ 5,473,356	$ 5,580,247
UNITED STATES
Segment Reporting Information [Line Items]
Revenue									5,310,573	5,094,193	5,189,792
CANADA
Segment Reporting Information [Line Items]
Revenue									180,951	116,491	114,451
Other Countries [Member]
Segment Reporting Information [Line Items]
Revenue									$ 314,545	$ 262,672	$ 276,004