Industry Segment and Geographic Area Data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Mar. 31, 2014
Quarter ended:
Total revenues	$ 824,188	$ 748,957
Depreciation and amortization, net of (gains) losses on disposals	65,235	61,117
Interest expense	24,148	23,328
Pretax earnings (loss)	195,051	179,048
Income tax expense	70,577	66,080
Identifiable assets	6,528,682	5,578,762	5,998,978
United States [Member]
Quarter ended:
Total revenues	778,276	706,089
Depreciation and amortization, net of (gains) losses on disposals	64,040	59,170
Interest expense	24,019	23,186
Pretax earnings (loss)	186,907	171,756
Income tax expense	68,419	64,148
Identifiable assets	6,358,303	5,425,667
Canada [Member]
Quarter ended:
Total revenues	45,912	42,868
Depreciation and amortization, net of (gains) losses on disposals	1,195	1,947
Interest expense	129	142
Pretax earnings (loss)	8,144	7,292
Income tax expense	2,158	1,932
Identifiable assets	$ 170,379	$ 153,095