Fair Value Measurements (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Assets:
Restricted cash	$ 43,269	$ 42,594
Fair value measured on a recurring basis | Quoted prices in active markets (Level 1)
Assets:
Cash and cash equivalents	133,064
Restricted cash	43,269
Investments in lieu of retainage	12,412
Total assets	188,745
Fair value measured on a recurring basis | Significant other observable inputs (Level 2)
Assets:
Short-term investments	2,565
Investments in lieu of retainage	8,927
Total assets	11,492
Liabilities:
Interest rate swap contract	835
Total liabilities	835
Fair value measured on a recurring basis | Significant unobservable inputs (Level 3)
Assets:
Long-term investments - auction rate securities	46,283
Total assets	46,283
Liabilities:
Contingent consideration	48,395
Total liabilities	48,395
Total Carrying Value
Assets:
Cash and cash equivalents	133,064
Restricted cash	43,269
Short-term investments	2,565
Investments in lieu of retainage	21,339
Long-term investments - auction rate securities	46,283
Total assets	246,520
Liabilities:
Interest rate swap contract	835
Contingent consideration	48,395
Total liabilities	$ 49,230